Organometallic Complex, Light-Emitting Element, Light-Emitting Device, Electronic Device, and Lighting Device

ABSTRACT

As a novel substance having a novel skeleton, an organometallic complex with high emission efficiency which achieves improved color purity by a reduction of half width of an emission spectrum is provided. One embodiment of the present invention is an organometallic complex in which a β-diketone and a six-membered heteroaromatic ring including two or more nitrogen atoms inclusive of a nitrogen atom that is a coordinating atom are ligands. In General Formula (G1), X represents a substituted or unsubstituted six-membered heteroaromatic ring including two or more nitrogen atoms inclusive of a nitrogen atom that is a coordinating atom. Further, R 1  to R 4  each represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

This application is a continuation of copending U.S. application Ser.No. 14/846,181, filed on Sep. 4, 2015 which is a continuation of U.S.application Ser. No. 13/716,811, filed on Dec. 17, 2012 (now U.S. Pat.No. 9,127,032 issued Sep. 8, 2015), which are all incorporated herein byreference.

TECHNICAL FIELD

One embodiment of the present invention relates to an organometalliccomplex. In particular, one embodiment of the present invention relatesto an organometallic complex that is capable of converting a tripletexcited state into luminescence. In addition, one embodiment of thepresent invention relates to a light-emitting element, a light-emittingdevice, an electronic device, and a lighting device each using anorganometallic complex.

BACKGROUND ART

Organic compounds are brought into an excited state by the absorption oflight. Through this excited state, various reactions (photochemicalreactions) are caused in some cases, or luminescence is generated insome cases. Therefore, the organic compounds have a wide range ofapplications.

As one example of the photochemical reactions, a reaction of singletoxygen with an unsaturated organic molecule (oxygen addition) is known.Since the ground state of an oxygen molecule is a triplet state, oxygenin a singlet state (singlet oxygen) is not generated by directphotoexcitation. However, in the presence of another triplet excitedmolecule, singlet oxygen is generated to cause an oxygen additionreaction. In this case, a compound capable of forming the tripletexcited molecule is referred to as a photosensitizer.

As described above, for generation of singlet oxygen, a photosensitizercapable of forming a triplet excited molecule by photoexcitation isneeded. However, the ground state of an ordinary organic compound is asinglet state; therefore, photoexcitation to a triplet excited state isforbidden transition and generation of a triplet excited molecule isdifficult. A compound that can easily cause intersystem crossing fromthe singlet excited state to the triplet excited state (or a compoundthat allows the forbidden transition of photoexcitation directly to thetriplet excited state) is thus required as such a photosensitizer. Inother words, such a compound can be used as the photosensitizer and isuseful.

The above compound often exhibits phosphorescence. Phosphorescencerefers to luminescence generated by transition between differentenergies in multiplicity. In an ordinary organic compound,phosphorescence refers to luminescence generated in returning from thetriplet excited state to the singlet ground state (in contrast,fluorescence refers to luminescence in returning from the singletexcited state to the singlet ground state). Application fields of acompound capable of exhibiting phosphorescence, that is, a compoundcapable of converting the triplet excited state into luminescence(hereinafter, referred to as a phosphorescent compound), include alight-emitting element including an organic compound as a light-emittingsubstance.

This light-emitting element has a simple structure in which alight-emitting layer including an organic compound that is alight-emitting substance is provided between electrodes. Thislight-emitting element has attracted attention as a next-generation flatpanel display element in terms of characteristics such as being thin andlight in weight, high speed response, and direct current low voltagedriving. Further, a display device including this light-emitting elementis superior in contrast, image quality, and wide viewing angle.

The light-emitting element including an organic compound as alight-emitting substance has a light emission mechanism that is of acarrier injection type: a voltage is applied between electrodes where alight-emitting layer is interposed, electrons and holes injected fromthe electrodes recombine to put the light-emitting substance into anexcited state, and then light is emitted in returning from the excitedstate to the ground state. As in the case of photoexcitation describedabove, types of the excited state include a singlet excited state (S*)and a triplet excited state (T*). The statistical generation ratiothereof in the light-emitting element is considered to be S*:T*=1:3.

At room temperature, a compound capable of converting a singlet excitedstate into luminescence (hereinafter, referred to as a fluorescentcompound) exhibits only luminescence from the singlet excited state(fluorescence), not luminescence from the triplet excited state(phosphorescence). Accordingly, the internal quantum efficiency (theratio of the number of generated photons to the number of injectedcarriers) of a light-emitting element including the fluorescent compoundis thought to have a theoretical limit of 25%, on the basis ofS*:T*=1:3.

On the other hand, in a case of a light-emitting element including thephosphorescent compound described above, the internal quantum efficiencythereof can be improved to 75% to 100% in theory; namely, the emissionefficiency thereof can be 3 to 4 times as much as that of thelight-emitting element including a fluorescent compound. Therefore, thelight-emitting element including a phosphorescent compound has beenactively developed in recent years in order to achieve a highlyefficient light-emitting element. An organometallic complex thatcontains iridium or the like as a central metal is particularlyattracting attention as a phosphorescent compound because of its highphosphorescence quantum yield (refer to Patent Document 1, PatentDocument 2, and Patent Document 3).

REFERENCE Patent Document

-   [Patent Document 1] Japanese Published Patent Application No.    2007-137872-   [Patent Document 2] Japanese Published Patent Application No.    2008-069221-   [Patent Document 3] International Publication WO 2008/035664    Pamphlet

DISCLOSURE OF INVENTION

While phosphorescent materials emitting various colors have beendeveloped as reported in Patent Documents 1 to 3, not many redlight-emitting materials achieving high color purity have been reported.

In view of the above, according to one embodiment of the presentinvention, as a novel substance having a novel skeleton, anorganometallic complex with high emission efficiency which achievesimproved color purity by a reduction of half width of an emissionspectrum is provided. Further, a novel organometallic complex with anexcellent sublimation property is provided. A light-emitting element, alight-emitting device, an electronic device, or a lighting device withhigh emission efficiency is provided.

One embodiment of the present invention is an organometallic complex inwhich a β-diketone and a six-membered heteroaromatic ring including twoor more nitrogen atoms inclusive of a nitrogen atom that is acoordinating atom are ligands. Therefore, one embodiment of the presentinvention is an organometallic complex having a structure represented byGeneral Formula (G1).

In the formula, X represents a substituted or unsubstituted six-memberedheteroaromatic ring including two or more nitrogen atoms inclusive of anitrogen atom that is a coordinating atom. Examples of a substituentbonded to X include a substituted or unsubstituted alkyl group having 1to 6 carbon atoms, a substituted or unsubstituted phenyl group, and aphenyl group having a substituted or unsubstituted alkyl group having 1to 6 carbon atoms. Further, R¹ to R⁴ each represent a substituted orunsubstituted alkyl group having 1 to 6 carbon atoms.

In General Formula (G1), R¹ and R² each represent a substituted orunsubstituted alkyl group having 1 to 6 carbon atoms, whereby a dihedralangle formed by carbon atoms of the benzene ring bonded to iridium canbe large. By increasing the dihedral angle, a secondary peak in anemission spectrum of the organometallic complex can be theoreticallyreduced as described later, whereby half width can be reduced. Note thatit is particularly preferable that R¹ and R² each represent a methylgroup.

In the above structure, the substituted or unsubstituted six-memberedheteroaromatic ring including the two or more nitrogen atoms inclusiveof the nitrogen atom that is the coordinating atom is preferablyrepresented by any one of General Formulae (X1) to (X4).

Note that in the formulae, R⁵ to R¹⁵ separately represent hydrogen, asubstituted or unsubstituted alkyl group having 1 to 6 carbon atoms, ora substituted or unsubstituted phenyl group. Examples of a substituentbonded to the phenyl group include a substituted or unsubstituted alkylgroup having 1 to 6 carbon atoms.

Another embodiment of the present invention is an organometallic complexrepresented by General Formula (G2).

In the formula, R¹ to R⁴ each represent a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms, and R⁵ to R⁷ separatelyrepresent a substituted or unsubstituted alkyl group having 1 to 6carbon atoms, or a substituted or unsubstituted phenyl group. Note thatR⁵ and R⁶ may represent hydrogen.

Another embodiment of the present invention is an organometallic complexrepresented by General Formula (G3).

In the formula, R¹ to R⁴ each represent a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms. Further, R⁸ to R¹⁰ separatelyrepresent a substituted or unsubstituted alkyl group having 1 to 6carbon atoms, or a substituted or unsubstituted phenyl group. R⁸ and R¹⁰may represent hydrogen.

Another embodiment of the present invention is an organometallic complexrepresented by General Formula (G4).

In the formula, R¹ to R⁴ each represent a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms. Further, R¹¹ to R¹³ separatelyrepresent hydrogen, a substituted or unsubstituted alkyl group having 1to 6 carbon atoms, or a substituted or unsubstituted phenyl group. R¹¹may represent hydrogen, and it is preferable that either R¹² or R¹³represent hydrogen.

Another embodiment of the present invention is an organometallic complexrepresented by General Formula (G5).

In the formula, R¹ to R⁴ each represent a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms. Further, R¹⁴ and R¹⁵ separatelyrepresent a substituted or unsubstituted alkyl group having 1 to 6carbon atoms, or a substituted or unsubstituted phenyl group. Note thatR¹⁴ and R¹⁵ may represent hydrogen.

Another embodiment of the present invention is an organometallic complexrepresented by Structural Formula (100).

Another embodiment of the present invention is an organometallic complexrepresented by Structural Formula (107).

Another embodiment of the present invention is an organometallic complexrepresented by Structural Formula (108).

Another embodiment of the present invention is an organometallic complexrepresented by Structural Formula (109).

Further, the organometallic complex of one embodiment of the presentinvention is very effective for the following reason: the organometalliccomplex can emit phosphorescence, that is, it can provide luminescencefrom a triplet excited state and can exhibit emission, and thereforehigher efficiency is possible when the organometallic complex is appliedto a light-emitting element. Thus, one embodiment of the presentinvention also includes a light-emitting element in which theorganometallic complex of one embodiment of the present invention isused.

Further, another embodiment of the present invention is a light-emittingelement which uses an organometallic complex having the structurerepresented by General Formula (G0) as a light-emitting substance.

In the formula, X represents a substituted or unsubstituted six-memberedheteroaromatic ring including two or more nitrogen atoms inclusive of anitrogen atom that is a coordinating atom. Examples of a substituentbonded to X include a substituted or unsubstituted alkyl group having 1to 6 carbon atoms, a substituted or unsubstituted phenyl group, and aphenyl group having a substituted or unsubstituted alkyl group having 1to 6 carbon atoms. Further, R¹ and R² each represent a substituted orunsubstituted alkyl group having 1 to 6 carbon atoms.

In General Formula (G0), R¹ and R² each represent a substituted orunsubstituted alkyl group having 1 to 6 carbon atoms, whereby a dihedralangle formed by carbon atoms of the benzene ring bonded to iridium canbe large. By increasing the dihedral angle, a secondary peak in anemission spectrum of the organometallic complex can be theoreticallyreduced as described later, whereby half width can be reduced. Thiseffect can be theoretically brought about in any light-emitting materialregardless of its skeleton as long as the light-emitting material hasthe structure represented by General Formula (G0) and emits lightderived from the structure. Therefore, light-emitting materials(including polymers and composite materials) which have the structurerepresented by General Formula (G0) and emit light derived from thestructure are embodiments of the present invention. In addition, alight-emitting element which uses a light-emitting material having thestructure represented by General Formula (G0) and emitting light derivedfrom the structure as a light-emitting substance is one embodiment ofthe present invention. Note that it is particularly preferable that R¹and R² each represent a methyl group.

In the above structure, the substituted or unsubstituted six-memberedheteroaromatic ring including the two or more nitrogen atoms inclusiveof the nitrogen atom that is the coordinating atom is preferablyrepresented by any one of General Formulae (X1) to (X4).

Note that in the formulae, R⁵ to R¹⁵ separately represent hydrogen, asubstituted or unsubstituted alkyl group having 1 to 6 carbon atoms, ora substituted or unsubstituted phenyl group. Examples of a substituentbonded to the phenyl group include a substituted or unsubstituted alkylgroup having 1 to 6 carbon atoms.

Other embodiments of the present invention are not only a light-emittingdevice including the light-emitting element but also an electronicdevice and a lighting device each including the light-emitting device.The light-emitting device in this specification refers to an imagedisplay device and a light source (e.g., a lighting device). Inaddition, the light-emitting device includes, in its category, all of amodule in which a light-emitting device is connected to a connector suchas a flexible printed circuit (FPC) or a tape carrier package (TCP), amodule in which a printed wiring board is provided on the tip of a TCP,and a module in which an integrated circuit (IC) is directly mounted ona light-emitting element by a chip on glass (COG) method.

According to one embodiment of the present invention, as a novelsubstance having a novel skeleton, an organometallic complex with highemission efficiency which achieves improved color purity by a reductionof half width of an emission spectrum can be provided. Further, a novelorganometallic complex with an excellent sublimation property can beprovided. With the use of the novel organometallic complex, alight-emitting element, a light-emitting device, an electronic device,or a lighting device with high emission efficiency can be provided.Alternatively, it is possible to provide a light-emitting element, alight-emitting device, an electronic device, or a lighting device withlow power consumption.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a structure of a light-emitting element.

FIG. 2 illustrates a structure of a light-emitting element.

FIGS. 3A and 3B illustrate structures of light-emitting elements.

FIG. 4 illustrates a light-emitting device.

FIGS. 5A and 5B illustrate a light-emitting device.

FIGS. 6A to 6D illustrate electronic devices.

FIGS. 7A to 7C illustrate an electronic device.

FIG. 8 illustrates lighting devices.

FIG. 9 shows a ¹H-NMR chart of an organometallic complex represented byStructural Formula (100).

FIG. 10 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of an organometallic complex represented by Structural Formula(100).

FIG. 11 shows a ¹H-NMR chart of an organometallic complex represented byStructural Formula (107).

FIG. 12 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of an organometallic complex represented by Structural Formula(107).

FIG. 13 shows a ¹H-NMR chart of an organometallic complex represented byStructural Formula (108).

FIG. 14 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of an organometallic complex represented by Structural Formula(108).

FIG. 15 illustrates a light-emitting element.

FIG. 16 shows current density-luminance characteristics of alight-emitting element 1.

FIG. 17 shows voltage-luminance characteristics of a light-emittingelement 1.

FIG. 18 shows luminance-current efficiency characteristics of alight-emitting element 1.

FIG. 19 shows voltage-current characteristics of a light-emittingelement 1.

FIG. 20 shows an emission spectrum of a light-emitting element 1.

FIG. 21 shows reliability of a light-emitting element 1.

FIG. 22 shows reliability of a light-emitting element 1.

FIG. 23 shows current density-luminance characteristics of alight-emitting element 2.

FIG. 24 shows voltage-luminance characteristics of a light-emittingelement 2.

FIG. 25 shows luminance-current efficiency characteristics of alight-emitting element 2.

FIG. 26 shows voltage-current characteristics of a light-emittingelement 2.

FIG. 27 shows an emission spectrum of a light-emitting element 2.

FIG. 28 shows reliability of a light-emitting element 2.

FIG. 29 shows reliability of a light-emitting element 2.

FIG. 30 shows current density-luminance characteristics of alight-emitting element 3.

FIG. 31 shows voltage-luminance characteristics of a light-emittingelement 3.

FIG. 32 shows luminance-current efficiency characteristics of alight-emitting element 3.

FIG. 33 shows voltage-current characteristics of a light-emittingelement 3.

FIG. 34 shows an emission spectrum of a light-emitting element 3.

FIG. 35 shows reliability of a light-emitting element 3.

FIG. 36 shows reliability of a light-emitting element 3.

FIG. 37 shows TG/DTA results of an organometallic complex represented byStructural Formula (100).

FIG. 38 shows phosphorescent spectra of [Ir(ppr)₂(acac)] (abbreviation)and [Ir(dmppr)₂(acac)] (abbreviation).

FIG. 39 shows results of a comparison of a dihedral angle formed bycarbon atoms of a benzene ring between [Ir(ppr)₂(acac)] (abbreviation)and [Ir(dmppr)₂(acac)] (abbreviation).

FIG. 40 shows a ¹H-NMR chart of an organometallic complex represented byStructural Formula (121).

FIG. 41 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of an organometallic complex represented by Structural Formula(121).

FIG. 42 shows TG/DTA results of an organometallic complex represented byStructural Formula (121).

FIG. 43 shows a ¹H-NMR chart of an organometallic complex represented byStructural Formula (122).

FIG. 44 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of an organometallic complex represented by Structural Formula(122).

FIG. 45 shows TG/DTA results of an organometallic complex represented byStructural Formula (122).

FIG. 46 shows LC/MS measurement results of an organometallic complexrepresented by Structural Formula (122).

FIG. 47 shows a ¹H-NMR chart of an organometallic complex represented byStructural Formula (123).

FIG. 48 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of an organometallic complex represented by Structural Formula(123).

FIG. 49 shows LC/MS measurement results of an organometallic complexrepresented by Structural Formula (123).

FIG. 50 shows a ¹H-NMR chart of an organometallic complex represented byStructural Formula (124).

FIG. 51 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of an organometallic complex represented by Structural Formula(124).

FIG. 52 shows TG/DTA results of an organometallic complex represented byStructural Formula (124).

FIG. 53 shows LC/MS measurement results of an organometallic complexrepresented by Structural Formula (124).

FIG. 54 shows a ¹H-NMR chart of an organometallic complex represented byStructural Formula (125).

FIG. 55 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of an organometallic complex represented by Structural Formula(125).

FIG. 56 shows TG/DTA results of an organometallic complex represented byStructural Formula (125).

FIG. 57 shows current density-luminance characteristics oflight-emitting elements 4 to 7.

FIG. 58 shows voltage-luminance characteristics of light-emittingelements 4 to 7.

FIG. 59 shows luminance-current efficiency characteristics oflight-emitting elements 4 to 7.

FIG. 60 shows voltage-current characteristics of light-emitting elements4 to 7.

FIG. 61 shows emission spectra of light-emitting elements 4 to 7.

FIG. 62 shows reliability of light-emitting elements 4 to 7.

FIG. 63 shows reliability of light-emitting elements 4 to 7.

FIG. 64 shows a ¹H-NMR chart of an organometallic complex represented byStructural Formula (126).

FIG. 65 shows a ¹H-NMR chart of an organometallic complex represented byStructural Formula (127).

FIG. 66 shows a ¹H-NMR chart of an organometallic complex represented byStructural Formula (106).

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. Note that thepresent invention is not limited to the description below, and modes anddetails thereof can be modified in various ways without departing fromthe spirit and the scope of the present invention. Therefore, thepresent invention should not be construed as being limited to thedescription of the following embodiments.

Embodiment 1

In this embodiment, organometallic complexes which are embodiments ofthe present invention will be described.

An organometallic complex that is one embodiment of the presentinvention is an organometallic complex in which a β-diketone and asix-membered heteroaromatic ring including two or more nitrogen atomsinclusive of a nitrogen atom that is a coordinating atom are ligands.Note that one mode of an organometallic complex which is described inthis embodiment and in which a β-diketone and a six-memberedheteroaromatic ring including two or more nitrogen atoms inclusive of anitrogen atom that is a coordinating atom are ligands is anorganometallic complex having the structure represented by GeneralFormula (G1).

In General Formula (G1), X represents a substituted or unsubstitutedsix-membered heteroaromatic ring including two or more nitrogen atomsinclusive of a nitrogen atom that is a coordinating atom. Further, R¹ toR⁴ each represent a substituted or unsubstituted alkyl group having 1 to6 carbon atoms.

Note that specific examples of the substituted or unsubstituted alkylgroup having 1 to 6 carbon atoms in R¹ to R⁴ include a methyl group, anethyl group, a propyl group, an isopropyl group, a butyl group, asec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group,an isopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentylgroup, a hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexylgroup, a neohexyl group, a 3-methylpentyl group, a 2-methylpentyl group,a 2-ethylbutyl group, a 1,2-dimethylbutyl group, and a 2,3-dimethylbutylgroup.

It is preferable that the substituted or unsubstituted six-memberedheteroaromatic ring X including the two or more nitrogen atoms inclusiveof the nitrogen atom that is the coordinating atom be, specifically,represented by any one of General Formulae (X1) to (X4).

Note that in an organometallic complex that is one embodiment of thepresent invention, two substituted or unsubstituted alkyl groups eachhaving 1 to 6 carbon atoms are bonded to the 2-position and the4-position of a phenyl group which is bonded to both metallic iridiumand a substituted or unsubstituted six-membered heteroaromatic ringincluding two or more nitrogen atoms inclusive of a nitrogen atom thatis a coordinating atom, which leads to a reduction in half width of anobtained emission spectrum so that the organometallic complex has anadvantage of achieving improved color purity. Moreover, the ligand has aβ-diketone structure, whereby solubility of the organometallic complexin an organic solvent is increased and purification is enhanced, whichis preferable. The β-diketone structure is preferably included forrealization of an organometallic complex with high emission efficiency.Inclusion of the β-diketone structure has advantages such as a highersublimation property and excellent evaporativity.

One embodiment of the present invention is an organometallic complexrepresented by General Formula (G2).

In General Formula (G2), R¹ to R⁴ each represent a substituted orunsubstituted alkyl group having 1 to 6 carbon atoms, and R⁵ to R⁷separately represent a substituted or unsubstituted alkyl group having 1to 6 carbon atoms, or a substituted or unsubstituted phenyl group. Notethat R⁵ and R⁶ may represent hydrogen. Specific examples of R¹ to R⁷include the specific examples of R¹ to R⁴ in General Formula (G1).Further, the substituted or unsubstituted phenyl group in R⁵ to R⁷ mayhave a substituted or unsubstituted alkyl group having 1 to 6 carbonatoms.

One embodiment of the present invention is an organometallic complexrepresented by General Formula (G3).

In General Formula (G3), R¹ to R⁴ each represent a substituted orunsubstituted alkyl group having 1 to 6 carbon atoms. Further, R⁸ to R¹⁰separately represent a substituted or unsubstituted alkyl group having 1to 6 carbon atoms, or a substituted or unsubstituted phenyl group. Notethat R⁸ and R¹⁰ may represent hydrogen. Specific examples of R¹ to R⁴and R⁸ to R¹⁰ include the specific examples of R¹ to R⁴ in GeneralFormula (G1). Further, the substituted or unsubstituted phenyl group inR⁸ to R¹⁰ may have a substituted or unsubstituted alkyl group having 1to 6 carbon atoms.

One embodiment of the present invention is an organometallic complexrepresented by General Formula (G4).

In General Formula (G4), R¹ to R⁴ each represent a substituted orunsubstituted alkyl group having 1 to 6 carbon atoms. Further, R¹¹ toR¹³ separately represent hydrogen, a substituted or unsubstituted alkylgroup having 1 to 6 carbon atoms, or a substituted or unsubstitutedphenyl group. Note that may represent hydrogen, and it is preferablethat either R¹² or R¹³ represent hydrogen. Specific examples of R¹ to R⁴and R¹¹ to R¹³ include the specific examples of R¹ to R⁴ in GeneralFormula (G1). Further, the substituted or unsubstituted phenyl group inR¹¹ to R¹³ may have a substituted or unsubstituted alkyl group having 1to 6 carbon atoms.

One embodiment of the present invention is an organometallic complexrepresented by General Formula (G5).

In General Formula (G5), R¹ to R⁴ each represent a substituted orunsubstituted alkyl group having 1 to 6 carbon atoms. Further, R¹⁴ andR¹⁵ separately represent a substituted or unsubstituted alkyl grouphaving 1 to 6 carbon atoms, or a substituted or unsubstituted phenylgroup. Note that R¹⁴ and R¹⁵ may represent hydrogen. Specific examplesof R¹ to R⁴, R¹⁴ and R¹⁵ include the specific examples of R¹ to R⁴ inGeneral Formula (G1). Further, the substituted or unsubstituted phenylgroup in R¹⁴ and R¹⁵ may have a substituted or unsubstituted alkyl grouphaving 1 to 6 carbon atoms.

Next, specific structural formulae of the above-described organometalliccomplexes each of which is one embodiment of the present invention willbe shown (Structural Formulae (100) to (127)). Note that the presentinvention is not limited thereto.

Note that organometallic complexes represented by Structural Formulae(100) to (127) are novel substances capable of emitting phosphorescence.Note that there can be geometrical isomers and stereoisomers of thesesubstances depending on the type of the ligand. The organometalliccomplex that is one embodiment of the present invention includes all ofthese isomers.

Next, an example of a method of synthesizing an organometallic complexhaving the structure represented by General Formula (G1) is described.

<<Method of Synthesizing a Six-Membered Heterocyclic DerivativeRepresented by General Formula (G0-X1)>>

An example of a method of synthesizing a six-membered heterocyclicderivative represented by General Formula (G0-X1) is described.

In General Formula (G0-X1), R¹, R², and R⁵ to R⁷ each represent asubstituted or unsubstituted alkyl group having 1 to 6 carbon atoms. R⁵and R⁶ may represent hydrogen.

Four Synthesis Schemes (A1), (A2), (A3), and (A4) of a pyrazinederivative represented by General Formula (G0-X1) which is asix-membered heterocycle are shown below.

In Synthesis Scheme (A1), a halide of 3,5-disubstituted phenyl (a1-1) islithiated with alkyl lithium or the like and reacted with pyrazine(a2-1) to yield the derivative (G0-X1).

In Synthesis Scheme (A2), a boronic acid of 3,5-disubstituted phenyl(a1-2) and a halide of pyrazine (a2-2) are coupled to yield thederivative (G0-X1).

In Synthesis Scheme (A3), a diketone of 3,5-disubstituted phenyl (a1-3)is reacted with diamine (a2-3) to yield the derivative (G0-X1).

In Synthesis Scheme (A4), pyrazine of 3,5-disubstituted phenyl (a1-4)and a lithium compound or a Grignard reagent (a2-4) are reacted to yieldthe derivative (G0-X1). Note that in the formula, Y represents a halogenelement.

Other than the above-described four methods, there are a plurality ofknown methods of synthesizing the derivative (G0-X1). Thus, any of themethods can be employed.

Since the compounds (a1-1), (a2-1), (a1-2), (a2-2), (a1-3), (a2-3),(a1-4), and (a2-4) in the above schemes have many varieties which arecommercially available or their synthesis is feasible, a great varietyof pyrazine derivatives can be synthesized as the pyrazine derivativerepresented by General Formula (G0-X1). Thus, a feature of theorganometallic complex which is one embodiment of the present inventionis the abundance of ligand variations.

<<Method of Synthesizing an Organometallic Complex of One Embodiment ofthe Present Invention Represented by General Formula (G1)>>

Next, a synthesis method of the organometallic complex which is oneembodiment of the present invention represented by General Formula (G1)and which is formed using the six-membered heterocyclic derivativerepresented by General Formula (G0) will be described.

Note that in General Formula (G1), X represents a substituted orunsubstituted six-membered heteroaromatic ring including two or morenitrogen atoms inclusive of a nitrogen atom that is a coordinating atom.Further, R¹ to R⁴ each represent a substituted or unsubstituted alkylgroup having 1 to 6 carbon atoms.

Synthesis Scheme (B) of the organometallic complex represented byGeneral Formula (G1) is shown below.

Note that in Synthesis Scheme (B), X represents a substituted orunsubstituted six-membered heteroaromatic ring including two or morenitrogen atoms inclusive of a nitrogen atom that is a coordinating atom.Further, Y represents a halogen, and R¹ and R² each represent asubstituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

As shown in Synthesis Scheme (B), a six-membered heterocyclic derivativerepresented by General Formula (LG0) and an iridium compound whichcontains a halogen (e.g., iridium chloride, iridium bromide, or iridiumiodide) are heated in an inert gas atmosphere by using no solvent, analcohol-based solvent (e.g., glycerol, ethylene glycol,2-methoxyethanol, or 2-ethoxyethanol) alone, or a mixed solvent of waterand one or more of the alcohol-based solvents, whereby a dinuclearcomplex (P), which is one type of an organometallic complex including ahalogen-bridged structure, can be obtained.

There is no particular limitation on a heating means, and an oil bath, asand bath, or an aluminum block may be used. Alternatively, microwavescan be used as a heating means.

Further, as shown in Synthesis Scheme (C), the dinuclear complex (P)obtained in Synthesis Scheme (B) is reacted with a β-diketone derivativein an inert gas atmosphere, whereby a proton of the β-diketonederivative is eliminated and a monoanionic β-diketone derivativecoordinates to the central metal, iridium. Thus, the organometalliccomplex that is one embodiment of the present invention, represented byGeneral Formula (G1), can be obtained.

Note that in Synthesis Scheme (C), X represents a substituted orunsubstituted six-membered heteroaromatic ring including two or morenitrogen atoms inclusive of a nitrogen atom that is a coordinating atom.Further, Y represents a halogen, and R¹ to R⁴ each represent asubstituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

There is no particular limitation on a heating means, and an oil bath, asand bath, or an aluminum block may be used. Alternatively, microwavescan be used as, a heating means.

The above is the description of the example of a method of synthesizingan organometallic complex that is one embodiment of the presentinvention; however, the present invention is not limited thereto and anyother synthesis method may be employed.

The above-described organometallic complex that is one embodiment of thepresent invention can emit phosphorescence and thus can be used as alight-emitting material or a light-emitting substance of alight-emitting element.

With the use of the organometallic complex that is one embodiment of thepresent invention, a light-emitting element, a light-emitting device, anelectronic device, or a lighting device with high emission efficiencycan be obtained. Alternatively, it is possible to obtain alight-emitting element, a light-emitting device, an electronic device,or a lighting device with low power consumption.

The structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments.

Embodiment 2

In this embodiment, a light-emitting element in which the organometalliccomplex described in Embodiment 1 as one embodiment of the presentinvention is used for a light-emitting layer is described with referenceto FIG. 1.

In a light-emitting element described in this embodiment, as illustratedin FIG. 1, an EL layer 102 including a light-emitting layer 113 isprovided between a pair of electrodes (a first electrode (anode) 101 anda second electrode (cathode) 103), and the EL layer 102 includes ahole-injection layer 111, a hole-transport layer 112, anelectron-transport layer 114, an electron-injection layer 115, a chargegeneration layer (E) 116, and the like in addition to the light-emittinglayer 113.

By application of a voltage to such a light-emitting element, holesinjected from the first electrode 101 side and electrons injected fromthe second electrode 103 side recombine in the light-emitting layer 113to raise the organometallic complex to an excited state. Then, light isemitted when the organometallic complex in the excited state returns tothe ground state. Thus, the organometallic complex of one embodiment ofthe present invention functions as a light-emitting substance in thelight-emitting element.

The hole-injection layer 111 included in the EL layer 102 is a layercontaining a substance having a high hole-transport property and anacceptor substance. When electrons are extracted from the substancehaving a high hole-transport property owing to the acceptor substance,holes are generated. Thus, holes are injected from the hole-injectionlayer 111 into the light-emitting layer 113 through the hole-transportlayer 112.

The charge generation layer (E) 116 is a layer containing a substancehaving a high hole-transport property and an acceptor substance. Owingto the acceptor substance, electrons are extracted from the substancehaving a high hole-transport property and the extracted electrons areinjected from the electron-injection layer 115 having anelectron-injection property into the light-emitting layer 113 throughthe electron-transport layer 114.

A specific example in which the light-emitting element described in thisembodiment is manufactured is described.

For the first electrode (anode) 101 and the second electrode (cathode)103, a metal, an alloy, an electrically conductive compound, a mixturethereof, and the like can be used. Specifically, indium oxide-tin oxide(ITO: indium tin oxide), indium oxide-tin oxide containing silicon orsilicon oxide, indium oxide-zinc oxide (indium zinc oxide), indium oxidecontaining tungsten oxide and zinc oxide, gold (Au), platinum (Pt),nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe),cobalt (Co), copper (Cu), palladium (Pd), and titanium (Ti) can be used.In addition, an element belonging to Group 1 or Group 2 of the periodictable, for example, an alkali metal such as lithium (Li) or cesium (Cs),an alkaline earth metal such as calcium (Ca) or strontium (Sr),magnesium (Mg), an alloy containing such an element (MgAg, AlLi), a rareearth metal such as europium (Eu) or ytterbium (Yb), an alloy containingsuch an element, graphene, and the like can be used. The first electrode(anode) 101 and the second electrode (cathode) 103 can be formed by, forexample, a sputtering method, an evaporation method (including a vacuumevaporation method), or the like.

As the substance having a high hole-transport property which is used forthe hole-injection layer 111, the hole-transport layer 112, and thecharge generation layer (E) 116, the following can be given, forexample: aromatic amine compounds such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD), 4,4′,4″-tris(carbazol-9-yl)triphenylamine(abbreviation: TCTA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA), and4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB);3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1);3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2);3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1); and the like. In addition, the followingcarbazole derivatives and the like can be used:4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), and9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA).The substances mentioned here are mainly ones that have a hole mobilityof 10⁻⁶ cm²Ns or higher. Note that any substance other than the abovesubstances may be used as long as the hole-transport property is higherthan the electron-transport property.

Further, a high molecular compound such as poly(N-vinylcarbazole)(abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyemethacrylamide](abbreviation: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:Poly-TPD) can be used.

As examples of the acceptor substance that is used for thehole-injection layer 111 and the charge generation layer (E) 116, atransition metal oxide or an oxide of a metal belonging to any of Group4 to Group 8 of the periodic table can be given. Specifically,molybdenum oxide is particularly preferable.

The light-emitting layer 113 contains the organometallic complexdescribed in Embodiment 1 as a guest material serving as alight-emitting substance and a substance that has higher tripletexcitation energy than this organometallic complex as a host material.

Preferable examples of the substance (i.e., host material) used fordispersing any of the above-described organometallic complexes include:any of compounds having an arylamine skeleton, such as2,3-bis(4-diphenylaminophenyl)quinoxaline (abbreviation: TPAQn) and NPB,carbazole derivatives such as CBP and4,4′,4″-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), andmetal complexes such as bis[2-(2-hydroxyphenyl)pyridinato]zinc(abbreviation: Znpp₂), bis[2-(2-hydroxyphenyl)benzoxazolato]zinc(abbreviation: Zn(BOX)₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation:BAlq), and tris(8-quinolinolato)aluminum (abbreviation: Alq₃).Alternatively, a high molecular compound such as PVK can be used.

Note that in the case where the light-emitting layer 113 contains theabove-described organometallic complex (guest material) and the hostmaterial, phosphorescence with high emission efficiency can be obtainedfrom the light-emitting layer 113.

The electron-transport layer 114 is a layer containing a substancehaving a high electron-transport property. For the electron-transportlayer 114, metal complexes such as Alg₃,tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq₂), BAlq,Zn(BOX)₂, or bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation:Zn(BTZ)₂) can be used. Alternatively, a heteroaromatic compound such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP), or4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs) can beused. Further alternatively, a high molecular compound such aspoly(2,5-pyridinediyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) can be used. The substances mentioned here aremainly ones that have an electron mobility of 10⁻⁶ cm²/Vs or higher.Note that any substance other than the above substances may be used forthe electron-transport layer 114 as long as the electron-transportproperty is higher than the hole-transport property.

Further, the electron-transport layer 114 is not limited to a singlelayer, and a stacked layer in which two or more layers containing any ofthe above-described substances are stacked may be used.

The electron-injection layer 115 is a layer containing a substancehaving a high electron-injection property. For the electron-injectionlayer 115, an alkali metal, an alkaline earth metal, or a compoundthereof, such as lithium fluoride (LiF), cesium fluoride (CsF), calciumfluoride (CaF₂), or lithium oxide (LiOx), can be used. Alternatively, arare earth metal compound such as erbium fluoride (ErF₃) can be used.Further alternatively, the substances for forming the electron-transportlayer 114, which are described above, can be used.

Alternatively, a composite material in which an organic compound and anelectron donor (donor) are mixed may be used for the electron-injectionlayer 115. Such a composite material is excellent in anelectron-injection property and an electron-transport property becauseelectrons are generated in the organic compound by the electron donor.In this case, the organic compound is preferably a material excellent intransporting the generated electrons. Specifically, for example, thesubstances for forming the electron-transport layer 114 (e.g., a metalcomplex and a heteroaromatic compound), which are described above, canbe used. As the electron donor, a substance showing an electron-donatingproperty with respect to the organic compound may be used. Specifically,an alkali metal, an alkaline earth metal, and a rare earth metal arepreferable, and lithium, cesium, magnesium, calcium, erbium, ytterbium,and the like are given. In addition, alkali metal oxide or alkalineearth metal oxide such as lithium oxide, calcium oxide, barium oxide,and the like can be given. A Lewis base such as magnesium oxide canalternatively be used. An organic compound such as tetrathiafulvalene(abbreviation: TTF) can alternatively be used.

Note that each of the above-described hole-injection layer 111,hole-transport layer 112, light-emitting layer 113, electron-transportlayer 114, electron-injection layer 115, and charge generation layer (E)116 can be formed by a method such as an evaporation method (e.g., avacuum evaporation method), an ink jet method, or a coating method.

In the above-described light-emitting element, current flows due to apotential difference generated between the first electrode 101 and thesecond electrode 103 and holes and electrons recombine in the EL layer102, whereby light is emitted. Then, the emitted light is extractedoutside through one or both of the first electrode 101 and the secondelectrode 103. Therefore, one or both of the first electrode 101 and thesecond electrode 103 are electrodes having a light-transmittingproperty.

The above-described light-emitting element can emit phosphorescenceoriginating from the organometallic complex and thus can have higherefficiency than a light-emitting element using a fluorescent compound.

Note that the light-emitting element described in this embodiment is anexample of a light-emitting element manufactured using theorganometallic complex that is one embodiment of the present invention.Further, as a light-emitting device including the above light-emittingelement, a passive matrix light-emitting device and an active matrixlight-emitting device can be manufactured. It is also possible tomanufacture a light-emitting device with a microcavity structureincluding a light-emitting element which is a different light-emittingelement from the above light-emitting elements as described in anotherembodiment. Each of the above light-emitting devices is included in thepresent invention.

Note that there is no particular limitation on the structure of the TFTin the case of manufacturing the active matrix light-emitting device.For example, a staggered TFT or an inverted staggered TFT can be used asappropriate. Further, a driver circuit formed over a TFT substrate maybe formed of both an N-type TFT and a P-type TFT or only either anN-type TFT or a P-type TFT. Furthermore, there is also no particularlimitation on crystallinity of a semiconductor film used for the TFT.For example, an amorphous semiconductor film, a crystallinesemiconductor film, an oxide semiconductor film, or the like can beused.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments.

Embodiment 3

In this embodiment, as one embodiment of the present invention, alight-emitting element in which two or more kinds of organic compoundsas well as an organometallic complex are used for a light-emitting layeris described.

A light-emitting element described in this embodiment includes an ELlayer 203 between a pair of electrodes (an anode 201 and a cathode 202)as illustrated in FIG. 2. Note that the EL layer 203 includes at least alight-emitting layer 204 and may include a hole-injection layer, ahole-transport layer, an electron-transport layer, an electron-injectionlayer, a charge generation layer (E), and the like. Note that for thehole-injection layer, the hole-transport layer, the electron-transportlayer, the electron-injection layer, and the charge generation layer(E), the substances described in Embodiment 2 can be used.

The light-emitting layer 204 described in this embodiment contains aphosphorescent compound 205 using the organometallic complex describedin Embodiment 1, a first organic compound 206, and a second organiccompound 207. Note that the phosphorescent compound 205 is a guestmaterial in the light-emitting layer 204. Moreover, one of the firstorganic compound 206 and the second organic compound 207, the content ofwhich is higher than that of the other in the light-emitting layer 204,is a host material in the light-emitting layer 204.

When the light-emitting layer 204 has the structure in which the guestmaterial is dispersed in the host material, crystallization of thelight-emitting layer can be suppressed. Further, it is possible tosuppress concentration quenching due to high concentration of the guestmaterial, and thus the light-emitting element can have higher emissionefficiency.

Note that it is preferable that a triplet excitation energy level (T₁level) of each of the first organic compound 206 and the second organiccompound 207 be higher than that of the phosphorescent compound 205. Thereason for this is that, when the T₁ level of the first organic compound206 (or the second organic compound 207) is lower than that of thephosphorescent compound 205, the triplet excitation energy of thephosphorescent compound 205, which is to contribute to light emission,is quenched by the first organic compound 206 (or the second organiccompound 207) and accordingly the emission efficiency decreases.

Here, for improvement in efficiency of energy transfer from a hostmaterial to a guest material, Förster mechanism (dipole-dipoleinteraction) and Dexter mechanism (electron exchange interaction), whichare known as mechanisms of energy transfer between molecules, areconsidered. According to the mechanisms, it is preferable that anemission spectrum of a host material (a fluorescence spectrum in energytransfer from a singlet excited state, and a phosphorescence spectrum inenergy transfer from a triplet excited state) largely overlap with anabsorption spectrum of a guest material (specifically, a spectrum in anabsorption band on the longest wavelength (lowest energy) side).However, in general, it is difficult to obtain an overlap between afluorescence spectrum of a host material and an absorption spectrum inan absorption band on the longest wavelength (lowest energy) side of aguest material. The reason for this is as follows: if the fluorescencespectrum of the host material overlaps with the absorption spectrum inthe absorption band on the longest wavelength (lowest energy) side ofthe guest material, since a phosphorescence spectrum of the hostmaterial is located on a longer wavelength (lower energy) side than thefluorescence spectrum, the T₁ level of the host material becomes lowerthan the T₁ level of the phosphorescent compound and the above-describedproblem of quenching occurs; yet, when the host material is designed insuch a manner that the T₁ level of the host material is higher than theT₁ level of the phosphorescent compound in order to avoid the problem ofquenching, the fluorescence spectrum of the host material is shifted tothe shorter wavelength (higher energy) side, and thus the fluorescencespectrum does not have any overlap with the absorption spectrum in theabsorption band on the longest wavelength (lowest energy) side of theguest material. For that reason, in general, it is difficult to obtainan overlap between a fluorescence spectrum of a host material and anabsorption spectrum in an absorption band on the longest wavelength(lowest energy) side of a guest material so as to maximize energytransfer from a singlet excited state of a host material.

Thus, in this embodiment, a combination of the first organic compound206 and the second organic compound 207 preferably forms an exciplex(also referred to as excited complex). In that case, the first organiccompound 206 and the second organic compound 207 form an exciplex at thetime of recombination of carriers (electrons and holes) in thelight-emitting layer 204. Thus, in the light-emitting layer 204, afluorescence spectrum of the first organic compound 206 and that of thesecond organic compound 207 are converted into an emission spectrum ofthe exciplex which is located on a longer wavelength side. Moreover,when the first organic compound 206 and the second organic compound 207are selected in such a manner that the emission spectrum of the exciplexlargely overlaps with the absorption spectrum of the guest material,energy transfer from a singlet excited state can be maximized. Note thatalso in the case of a triplet excited state, energy transfer from theexciplex, not the host material, is presumed to occur.

For the phosphorescent compound 205, the organometallic complexdescribed in Embodiment 1 is used. Although the combination of the firstorganic compound 206 and the second organic compound 207 can bedetermined such that an exciplex is formed, a combination of a compoundwhich is likely to accept electrons (a compound having anelectron-trapping property) and a compound which is likely to acceptholes (a compound having a hole-trapping property) is preferablyemployed.

As examples of a compound which is likely to accept electrons, thefollowing can be given:2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II),2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline(abbreviation: 2CzPDBq-III),7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:7mDBTPDBq-II), and6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:6mDBTPDBq-II).

As examples of a compound which is likely to accept holes, the followingcan be given: 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBA1BP),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1),4,4′,4″-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation:1′-TNATA),2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9′-bifluorene(abbreviation: DPA2SF),N,N′-bis(9-phenylcarbazol-3-yl)-N,N′-diphenylbenzene-1,3-diamine(abbreviation: PCA2B),N-(9,9-dimethyl-2-N′,N′-diphenylamino-9H-fluoren-7-yl)diphenylamine(abbreviation: DPNF),N,N′,N″-triphenyl-N,N′,N″-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine(abbreviation: PCA3B),2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: PCASF),2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: DPASF),N,N′-bis[4-(carbazol-9-yl)phenyl]-N,N′-diphenyl-9,9-dimethylfluorene-2,7-diamine(abbreviation: YGA2F),4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (abbreviation: TPD),4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB),N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N-phenyl-N-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine(abbreviation: DFLADFL),3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA1),3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA2),4,4′-bis(N-{4-[N′-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl(abbreviation: DNTPD),3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole(abbreviation: PCzTPN2), and3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2).

As for the above-described first and second organic compounds 206 and207, the present invention is not limited to the above examples. Thecombination is determined so that an exciplex can be formed, theemission spectrum of the exciplex overlaps with the absorption spectrumof the phosphorescent compound 205, and the peak of the emissionspectrum of the exciplex has a longer wavelength than the peak of theabsorption spectrum of the phosphorescent compound 205.

Note that in the case where a compound which is likely to acceptelectrons and a compound which is likely to accept holes are used forthe first organic compound 206 and the second organic compound 207,carrier balance can be controlled by the mixture ratio of the compounds.Specifically, the ratio of the first organic compound to the secondorganic compound is preferably 1:9 to 9:1.

In the light-emitting element described in this embodiment, energytransfer efficiency can be improved owing to energy transfer utilizingan overlap between an emission spectrum of an exciplex and an absorptionspectrum of a phosphorescent compound; accordingly, it is possible toachieve high external quantum efficiency of the light-emitting element.

Note that in another structure of the present invention, thelight-emitting layer 204 can be formed using a host molecule having ahole-trapping property and a host molecule having an electron-trappingproperty as the two kinds of organic compounds (the first organiccompound 206 and the second organic compound 207) other than thephosphorescent compound 205 (guest material) so that a phenomenon (guestcoupled with complementary hosts: GCCH) occurs in which holes andelectrons are introduced to guest molecules existing in the two kinds ofhost molecules and the guest molecules are brought into an excitedstate.

At this time, the host molecule having a hole-trapping property and thehost molecule having an electron-trapping property can be respectivelyselected from the above-described compounds which are likely to acceptholes and the above-described compounds which are likely to acceptelectrons.

Note that the light-emitting element described in this embodiment is anexample of a structure of a light-emitting element; it is possible toapply a light-emitting element having another structure, which isdescribed in another embodiment, to a light-emitting device that is oneembodiment of the present invention. Further, as a light-emitting deviceincluding the above light-emitting element, a passive matrixlight-emitting device and an active matrix light-emitting device can bemanufactured. It is also possible to manufacture a light-emitting devicewith a microcavity structure including a light-emitting element which isa different light-emitting element from the above light-emittingelements as described in another embodiment. Each of the abovelight-emitting devices is included in the present invention.

Note that there is no particular limitation on the structure of the TFTin the case of manufacturing the active matrix light-emitting device.For example, a staggered TFT or an inverted staggered TFT can be used asappropriate. Further, a driver circuit formed over a TFT substrate maybe formed of both an N-type TFT and a P-type TFT or only either anN-type TFT or a P-type TFT. Furthermore, there is also no particularlimitation on crystallinity of a semiconductor film used for the TFT.For example, an amorphous semiconductor film, a crystallinesemiconductor film, an oxide semiconductor film, or the like can beused.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments.

Embodiment 4

In this embodiment, as one embodiment of the present invention, alight-emitting element (hereinafter referred to as tandem light-emittingelement) in which a charge generation layer is provided between aplurality of EL layers is described.

A light-emitting element described in this embodiment is a tandemlight-emitting element including a plurality of EL layers (a first ELlayer 302(1) and a second EL layer 302(2)) between a pair of electrodes(a first electrode 301 and a second electrode 304) as illustrated inFIG. 3A.

In this embodiment, the first electrode 301 functions as an anode, andthe second electrode 304 functions as a cathode. Note that the firstelectrode 301 and the second electrode 304 can have structures similarto those described in Embodiment 2. In addition, although the pluralityof EL layers (the first EL layer 302(1) and the second EL layer 302(2))may have a structure similar to that of the EL layer described inEmbodiment 2 or 3, any of the EL layers may have a structure similar tothat of the EL layer described in Embodiment 2 or 3. In other words, thestructures of the first EL layer 302(1) and the second EL layer 302(2)may be the same or different from each other and can be similar to thatof the EL layer described in Embodiment 2 or 3.

Further, a charge generation layer (I) 305 is provided between theplurality of EL layers (the first EL layer 302(1) and the second ELlayer 302(2)). The charge generation layer (I) 305 has a function ofinjecting electrons into one of the EL layers and injecting holes intothe other of the EL layers when a voltage is applied between the firstelectrode 301 and the second electrode 304. In this embodiment, when avoltage is applied such that the potential of the first electrode 301 ishigher than that of the second electrode 304, the charge generationlayer (I) 305 injects electrons into the first EL layer 302(1) andinjects holes into the second EL layer 302(2).

Note that in terms of light extraction efficiency, the charge generationlayer (I) 305 preferably has a light-transmitting property with respectto Visible light (specifically, the charge generation layer (I) 305 hasa visible light transmittance of 40% or more). Further, the chargegeneration layer (I) 305 functions even if it has lower conductivitythan the first electrode 301 or the second electrode 304.

The charge generation layer (I) 305 may have either a structure in whichan electron acceptor (acceptor) is added to an organic compound having ahigh hole-transport property or a structure in which an electron donor(donor) is added to an organic compound having a high electron-transportproperty. Alternatively, both of these structures may be stacked.

In the case of the structure in which an electron acceptor is added toan organic compound having a high hole-transport property, as theorganic compound having a high hole-transport property, for example, anaromatic amine compound such as NPB, TPD, TDATA, MTDATA, or4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), or the like can be used. The substances mentionedhere are mainly ones that have a hole mobility of 10⁻⁶ cm²/Vs or higher.Note that any substance other than the above substances may be used aslong as they are organic compounds with a hole-transport property higherthan an electron-transport property.

Further, as the electron acceptor,7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ), chloranil, or the like can be used. Alternatively, atransition metal oxide can be used. Further alternatively, an oxide ofmetals that belong to Group 4 to Group 8 of the periodic table can beused. Specifically, it is preferable to use vanadium oxide, niobiumoxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide,manganese oxide, or rhenium oxide because the electron-acceptingproperty is high. Among these, molybdenum oxide is especially preferablebecause it is stable in the air, has a low hygroscopic property, and iseasily handled.

On the other hand, in the case of the structure in which an electrondonor is added to an organic compound having a high electron-transportproperty, as the organic compound having a high electron-transportproperty for example, a metal complex having a quinoline skeleton or abenzoquinoline skeleton, such as Alq, Almq₃, BeBq₂, or BAlq, or the likecan be used. Alternatively, it is possible to use a metal complex havingan oxazole-based ligand or a thiazole-based ligand, such as Zn(BOX)₂ orZn(BTZ)₂. Further alternatively, instead of a metal complex, it ispossible to use PBD, OXD-7, TAZ, BPhen, BCP, or the like. The substancesmentioned here are mainly ones that have an electron mobility of 10⁻⁶cm²/Vs or higher. Note that any substance other than the abovesubstances may be used as long as they are organic compounds with anelectron-transport property higher than a hole-transport property.

As the electron donor, it is possible to use an alkali metal, analkaline earth metal, a rare earth metal, a metal belonging to Group 2or 13 of the periodic table, or an oxide or a carbonate thereof.Specifically, it is preferable to use lithium (Li), cesium (Cs),magnesium (Mg), calcium (Ca), ytterbium (Yb), indium (In), lithiumoxide, cesium carbonate, or the like. Alternatively, an organic compoundsuch as tetrathianaphthacene may be used as the electron donor.

Note that forming the charge generation layer (I) 305 by using any ofthe above materials can suppress an increase in drive voltage caused bythe stack of the EL layers.

Although this embodiment shows the light-emitting element having two ELlayers, the present invention can be similarly applied to alight-emitting element in which n EL layers (302(1) to 302(n)) (n isthree or more) are stacked as illustrated in FIG. 3B. In the case wherea plurality of EL layers are included between a pair of electrodes as inthe light-emitting element according to this embodiment, by provision ofcharge generation layers (I) (305(1) to 305(n−1)) between the EL layers,light emission in a high luminance region can be obtained with currentdensity kept low. Since the current density can be kept low, the elementcan have a long lifetime. Further, in application to lighting devices, avoltage drop due to resistance of an electrode material can be reducedand accordingly homogeneous light emission in a large area is possible.Moreover, it is possible to achieve a light-emitting device of low powerconsumption, which can be driven at a low voltage.

By making the EL layers emit light of different colors from each other,the light-emitting element can provide light emission of a desired coloras a whole. For example, by forming a light-emitting element having twoEL layers such that the emission color of the first EL layer and theemission color of the second EL layer are complementary colors, thelight-emitting element can provide white light emission as a whole. Notethat the word “complementary” means color relationship in which anachromatic color is obtained when colors are mixed. In other words, whenlight obtained from a light-emitting substance and light of acomplementary color are mixed, white emission can be obtained.

Further, the same can be applied to a light-emitting element havingthree EL layers. For example, the light-emitting element as a whole canprovide white light emission when the emission color of the first ELlayer is red, the emission color of the second EL layer is green, andthe emission color of the third EL layer is blue.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments.

Embodiment 5

In this embodiment, a light-emitting device which is one embodiment ofthe present invention is described.

A light-emitting device described in this embodiment has a micro opticalresonator (microcavity) structure in which a light resonant effectbetween a pair of electrodes is utilized. The light-emitting deviceincludes a plurality of light-emitting elements each of which has atleast an EL layer 405 between a pair of electrodes (a reflectiveelectrode 401 and a semi-transmissive and semi-reflective electrode 402)as illustrated in FIG. 4. Further, the EL layer 405 includes at leastlight-emitting layers 404 (404R, 404G, and 404B) serving as alight-emitting region and may further include a hole-injection layer, ahole-transport layer, an electron-transport layer, an electron-injectionlayer, a charge generation layer (E), and the like. Note that thelight-emitting layer 404 contains the organometallic complex that is oneembodiment of the present invention.

In this embodiment, a light-emitting device is described which includeslight-emitting elements (a first light-emitting element (R) 410R, asecond light-emitting element (G) 410G, and a third light-emittingelement (B) 410B) having different structures as illustrated in FIG. 4.

The first light-emitting element (R) 410R has a structure in which afirst transparent conductive layer 403 a; an EL layer 405 including afirst light-emitting layer (B) 404B, a second light-emitting layer (G)404G, and a third light-emitting layer (R) 404R in part; and asemi-transmissive and semi-reflective electrode 402 are sequentiallystacked over a reflective electrode 401. The second light-emittingelement (G) 410G has a structure in which a second transparentconductive layer 403 b, the EL layer 405, and the semi-transmissive andsemi-reflective electrode 402 are sequentially stacked over thereflective electrode 401. The third light-emitting element (B) 410B hasa structure in which the EL layer 405 and the semi-transmissive andsemi-reflective electrode 402 are sequentially stacked over thereflective electrode 401.

Note that the reflective electrode 401, the EL layer 405, and thesemi-transmissive and semi-reflective electrode 402 are common to thelight-emitting elements (the first light-emitting element (R) 410R, thesecond light-emitting element (G) 410G, and the third light-emittingelement (B) 410B). The first light-emitting layer (B) 404B emits light(λ_(B)) having a peak in a wavelength region from 420 nm to 480 nm. Thesecond light-emitting layer (G) 404G emits light (λ_(G)) having a peakin a wavelength region from 500 nm to 550 nm. The third light-emittinglayer (R) 404R emits light (λ_(R)) having a peak in a wavelength regionfrom 600 nm to 760 nm. Thus, in each of the light-emitting elements (thefirst light-emitting element (R) 410R, the second light-emitting element(G) 410G, and the third light-emitting element (B) 410B), light emittedfrom the first light-emitting layer (B) 404B, light emitted from thesecond light-emitting layer (G) 404G, and light emitted from the thirdlight-emitting layer (R) 404R overlap with each other; accordingly,light having a broad emission spectrum that covers a visible lightregion can be emitted. Note that the above wavelengths satisfy therelation of λ_(B)<λ_(G)<λ_(R).

Each of the light-emitting elements described in this embodiment has astructure in which the EL layer 405 is interposed between the reflectiveelectrode 401 and the semi-transmissive and semi-reflective electrode402. Light emitted in all directions from the light-emitting layersincluded in the EL layer 405 is resonated by the reflective electrode401 and the semi-transmissive and semi-reflective electrode 402 whichfunction as a micro optical resonator (microcavity). Note that thereflective electrode 401 is formed using a conductive material havingreflectivity, and a film whose visible light reflectivity is 40% to100%, preferably 70% to 100%, and whose resistivity is 1×10⁻² Ωcm orlower is used. In addition, the semi-transmissive and semi-reflectiveelectrode 402 is formed using a conductive material having reflectivityand a conductive material having a light-transmitting property, and afilm whose visible light reflectivity is 20% to 80%, preferably 40% to70%, and whose resistivity is 1×10⁻² Ωcm or lower is used.

In this embodiment, the thicknesses of the transparent conductive layers(the first transparent conductive layer 403 a and the second transparentconductive layer 403 b) provided in the first light-emitting element (R)410R and the second light-emitting element (G) 410G, respectively, arevaried between the light-emitting elements, whereby the light-emittingelements differ from each other in the optical path length from thereflective electrode 401 to the semi-transmissive and semi-reflectiveelectrode 402. In other words, in light having a broad emissionspectrum, which is emitted from the light-emitting layers of each of thelight-emitting elements, light with a wavelength that is resonatedbetween the reflective electrode 401 and the semi-transmissive andsemi-reflective electrode 402 can be intensified while light with awavelength that is not resonated therebetween can be attenuated. Thus,when the elements differ from each other in the optical path length fromthe reflective electrode 401 to the semi-transmissive andsemi-reflective electrode 402, light with different wavelengths can beextracted.

Note that the optical path length (also referred to as optical distance)is expressed as a product of an actual distance and a refractive index,and in this embodiment, is a product of an actual thickness and n(refractive index). That is, an optical path length=actual thickness×n.

Further, the total thickness from the reflective electrode 401 to thesemi-transmissive and semi-reflective electrode 402 is set to mλ_(R)/2(m is a natural number) in the first light-emitting element (R) 410R;the total thickness from the reflective electrode 401 to thesemi-transmissive and semi-reflective electrode 402 is set to mλ_(G)/2(m is a natural number) in the second light-emitting element (G) 410G;and the total thickness from the reflective electrode 401 to thesemi-transmissive and semi-reflective electrode 402 is set to mλ_(B)/2(m is a natural number) in the third light-emitting element (B) 410B.

In this manner, the light (λ_(R)) emitted from the third light-emittinglayer (R) 404R included in the EL layer 405 is mainly extracted from thefirst light-emitting element (R) 410R, the light (λ_(G)) emitted fromthe second light-emitting layer (G) 404G included in the EL layer 405 ismainly extracted from the second light-emitting element (G) 410G, andthe light (λ_(B)) emitted from the first light-emitting layer (B) 404Bincluded in the EL layer 405 is mainly extracted from the thirdlight-emitting element (B) 410B. Note that the light extracted from eachof the light-emitting elements is emitted from the semi-transmissive andsemi-reflective electrode 402 side.

Further, strictly speaking, the total thickness from the reflectiveelectrode 401 to the semi-transmissive and semi-reflective electrode 402can be the total thickness from a reflection region in the reflectiveelectrode 401 to a reflection region in the semi-transmissive andsemi-reflective electrode 402. However, it is difficult to preciselydetermine the positions of the reflection regions in the reflectiveelectrode 401 and the semi-transmissive and semi-reflective electrode402; therefore, it is presumed that the above effect can be sufficientlyobtained wherever the reflection regions may be set in the reflectiveelectrode 401 and the semi-transmissive and semi-reflective electrode402.

Next, in the first light-emitting element (R) 410R, the optical pathlength from the reflective electrode 401 to the third light-emittinglayer (R) 404R is adjusted to a desired thickness ((2m′+1)λ_(R)/4, wherem′ is a natural number); thus, light emitted from the thirdlight-emitting layer (R) 404R can be amplified. Light (first reflectedlight) that is reflected by the reflective electrode 401 of the lightemitted from the third light-emitting layer (R) 404R interferes withlight (first incident light) that directly enters the semi-transmissiveand semi-reflective electrode 402 from the third light-emitting layer(R) 404R. Therefore, by adjusting the optical path length from thereflective electrode 401 to the third light-emitting layer (R) 404R tothe desired value ((2m′+1)λ_(R)/4, where m′ is a natural number), thephases of the first reflected light and the first incident light can bealigned with each other and the light emitted from the thirdlight-emitting layer (R) 404R can be amplified.

Note that strictly speaking, the optical path length from the reflectiveelectrode 401 to the third light-emitting layer (R) 404R can be theoptical path length from a reflection region in the reflective electrode401 to a light-emitting region in the third light-emitting layer (R)404R. However, it is difficult to precisely determine the positions ofthe reflection region in the reflective electrode 401 and thelight-emitting region in the third light-emitting layer (R) 404R;therefore, it is presumed that the above effect can be sufficientlyobtained wherever the reflection region and the light-emitting regionmay be set in the reflective electrode 401 and the third light-emittinglayer (R) 404R, respectively.

Next, in the second light-emitting element (G) 410G, the optical pathlength from the reflective electrode 401 to the second light-emittinglayer (G) 404G is adjusted to a desired thickness ((2m″+1)λ_(G)/4, wherem″ is a natural number); thus, light emitted from the secondlight-emitting layer (G) 404G can be amplified. Light (second reflectedlight) that is reflected by the reflective electrode 401 of the lightemitted from the second light-emitting layer (G) 404G interferes withlight (second incident light) that directly enters the semi-transmissiveand semi-reflective electrode 402 from the second light-emitting layer(G) 404G. Therefore, by adjusting the optical path length from thereflective electrode 401 to the second light-emitting layer (G) 404G tothe desired value ((2m″+1)λ_(G)/4, where m″ is a natural number), thephases of the second reflected light and the second incident light canbe aligned with each other and the light emitted from the secondlight-emitting layer (G) 404G can be amplified.

Note that strictly speaking, the optical path length from the reflectiveelectrode 401 to the second light-emitting layer (G) 404G can be theoptical path length from a reflection region in the reflective electrode401 to a light-emitting region in the second light-emitting layer (G)404G. However, it is difficult to precisely determine the positions ofthe reflection region in the reflective electrode 401 and thelight-emitting region in the second light-emitting layer (G) 404G;therefore, it is presumed that the above effect can be sufficientlyobtained wherever the reflection region and the light-emitting regionmay be set in the reflective electrode 401 and the second light-emittinglayer (G) 404G, respectively.

Next, in the third light-emitting element (B) 410B, the optical pathlength from the reflective electrode 401 to the first light-emittinglayer (B) 404B is adjusted to a desired thickness ((2m′″+1)λ_(B)/4,where in m′″ is a natural number); thus, light emitted from the firstlight-emitting layer (B) 404B can be amplified. Light (third reflectedlight) that is reflected by the reflective electrode 401 of the lightemitted from the first light-emitting layer (B) 404B interferes withlight (third incident light) that directly enters the semi-transmissiveand semi-reflective electrode 402 from the first light-emitting layer(B) 404B. Therefore, by adjusting the optical path length from thereflective electrode 401 to the first light-emitting layer (B) 404B tothe desired value ((2m′″+1)λ_(B)/4, where m′″ is a natural number), thephases of the third reflected light and the third incident light can bealigned with each other and the light emitted from the firstlight-emitting layer (B) 404B can be amplified.

Note that strictly speaking, the optical path length from the reflectiveelectrode 401 to the first light-emitting layer (B) 404B in the thirdlight-emitting element can be the optical path length from a reflectionregion in the reflective electrode 401 to a light-emitting region in thefirst light-emitting layer (B) 404B. However, it is difficult toprecisely determine the positions of the reflection region in thereflective electrode 401 and the light-emitting region in the firstlight-emitting layer (B) 404B; therefore, it is presumed that the aboveeffect can be sufficiently obtained wherever the reflection region andthe light-emitting region may be set in the reflective electrode 401 andthe first light-emitting layer (B) 404B, respectively.

Note that although each of the light-emitting elements in theabove-described structure includes a plurality of light-emitting layersin the EL layer, the present invention is not limited thereto; forexample, the structure of the tandem light-emitting element which isdescribed in Embodiment 4 can be combined, in which case a plurality ofEL layers and a charge generation layer interposed therebetween areprovided in one light-emitting element and one or more light-emittinglayers are formed in each of the EL layers.

The light-emitting device described in this embodiment has a microcavitystructure, in which light with wavelengths which differ depending on thelight-emitting elements can be extracted even when they include the sameEL layers, so that it is not needed to form light-emitting elements forthe colors of R, U, and B. Therefore, the above structure isadvantageous for full color display owing to easiness in achievinghigher resolution display or the like. In addition, emission intensitywith a predetermined wavelength in the front direction can be increased,whereby power consumption can be reduced. The above structure isparticularly useful in the case of being applied to a color display(image display device) including pixels of three or more colors but mayalso be applied to lighting or the like.

Embodiment 6

In this embodiment, a light-emitting device including a light-emittingelement in which the organometallic complex that is one embodiment ofthe present invention is used for a light-emitting layer is described.

The light-emitting device can be either a passive matrix light-emittingdevice or an active matrix light-emitting device. Note that any of thelight-emitting elements described in the other embodiments can beapplied to the light-emitting device described in this embodiment.

In this embodiment, an active matrix light-emitting device is describedwith reference to FIGS. 5A and 5B.

Note that FIG. 5A is a top view illustrating a light-emitting device andFIG. 5B is a cross-sectional view taken along the chain line A-A′ inFIG. 5A. The active matrix light-emitting device according to thisembodiment includes a pixel portion 502 provided over an elementsubstrate 501, a driver circuit portion (a source line driver circuit)503, and driver circuit portions (gate line driver circuits) 504 (504 aand 504 b). The pixel portion 502, the driver circuit portion 503, andthe driver circuit portions 504 are sealed between the element substrate501 and the sealing substrate 506 with a sealant 505.

In addition, a lead wiring 507 is provided over the element substrate501. The lead wiring 507 is provided for connecting an external inputterminal through which a signal (e.g., a video signal, a clock signal, astart signal, and a reset signal) or a potential from the outside istransmitted to the driver circuit portion 503 and the driver circuitportions 504. Here is shown an example in which a flexible printedcircuit (FPC) 508 is provided as the external input terminal. Althoughthe FPC 508 is illustrated alone, this FPC may be provided with aprinted wiring board (PWB). The light-emitting device in the presentspecification includes, in its category, not only the light-emittingdevice itself but also the light-emitting device provided with the FPCor the PWB.

Next, a cross-sectional structure is described with reference to FIG.5B. The driver circuit portion and the pixel portion are formed over theelement substrate 501; here are illustrated the driver circuit portion503 which is the source line driver circuit and the pixel portion 502.

The driver circuit portion 503 is an example where a CMOS circuit isformed, which is a combination of an n-channel TFT 509 and a p-channelTFT 510. Note that a circuit included in the driver circuit portion maybe formed using various CMOS circuits, PMOS circuits, or NMOS circuits.Although this embodiment shows a driver integrated type in which thedriver circuit is formed over the substrate, the driver circuit is notnecessarily formed over the substrate, and may be formed outside thesubstrate.

The pixel portion 502 is formed of a plurality of pixels each of whichincludes a switching TFT 511, a current control TFT 512, and a firstelectrode (anode) 513 which is electrically connected to a wiring (asource electrode or a drain electrode) of the current control TFT 512.Note that an insulator 514 is formed to cover end portions of the firstelectrode (anode) 513. In this embodiment, the insulator 514 is formedusing a positive photosensitive acrylic resin.

The insulator 514 preferably has a curved surface with curvature at anupper end portion or a lower end portion thereof in order to obtainfavorable coverage by a film which is to be stacked over the insulator514. For example, in the case of using a positive photosensitive acrylicresin as a material for the insulator 514, the insulator 514 preferablyhas a curved surface with a curvature radius (0.2 μm to 3 μm) at theupper end portion. Note that the insulator 514 can be formed usingeither a negative photosensitive resin or a positive photosensitiveresin. The material of the insulator 514 is not limited to an organiccompound and an inorganic compound such as silicon oxide or siliconoxynitride can also be used.

An EL layer 515 and a second electrode (cathode) 516 are stacked overthe first electrode (anode) 513. In the EL layer 515, at least alight-emitting layer is provided which contains the organometalliccomplex that is one embodiment of the present invention. Further, in theEL layer 515, a hole-injection layer, a hole-transport layer, anelectron-transport layer, an electron-injection layer, a chargegeneration layer, and the like can be provided as appropriate inaddition to the light-emitting layer.

A light-emitting element 517 is formed of a stacked structure of thefirst electrode (anode) 513, the EL layer 515, and the second electrode(cathode) 516. For the first electrode (anode) 513, the EL layer 515,and the second electrode (cathode) 516, the materials described inEmbodiment 2 can be used. Although not illustrated, the second electrode(cathode) 516 is electrically connected to the FPC 508 which is anexternal input terminal.

Although the cross-sectional view of FIG. 5B illustrates only onelight-emitting element 517, a plurality of light-emitting elements arearranged in matrix in the pixel portion 502. Light-emitting elementswhich provide three kinds of light emission (R, and B) are selectivelyformed in the pixel portion 502, whereby a light-emitting device capableof full color display can be fabricated. Alternatively, a light-emittingdevice which is capable of full color display may be fabricated by acombination with color filters.

Further, the sealing substrate 506 is attached to the element substrate501 with the sealant 505, whereby the light-emitting element 517 isprovided in a space 518 surrounded by the element substrate 501, thesealing substrate 506, and the sealant 505. The space 518 may be filledwith an inert gas (such as nitrogen or argon), or the sealant 505.

An epoxy-based resin is preferably used for the sealant 505. It ispreferable that such a material do not transmit moisture or oxygen asmuch as possible. As the sealing substrate 506, a glass substrate, aquartz substrate, or a plastic substrate formed of fiberglass reinforcedplastic (FRP), poly(vinyl fluoride) (PVF), polyester, acrylic, or thelike can be used.

As described above, an active matrix light-emitting device can beobtained.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments.

Embodiment 7

In this embodiment, examples of a variety of electronic devices whichare completed using a light-emitting device are described with referenceto FIGS. 6A to 6D and FIGS. 7A to 7C. To the light-emitting device, theorganometallic complex that is one embodiment of the present inventionis applied.

Examples of the electronic devices to which the light-emitting device isapplied are a television device (also referred to as television ortelevision receiver), a monitor of a computer or the like, a camera suchas a digital camera or a digital video camera, a digital photo frame, amobile phone (also referred to as cellular phone or cellular phonedevice), a portable game machine, a portable information terminal, anaudio reproducing device, and a large-sized game machine such as apachinko machine. Specific examples of these electronic devices areillustrated in FIGS. 6A to 6D.

FIG. 6A illustrates an example of a television set. In a television set7100, a display portion 7103 is incorporated in a housing 7101. Imagescan be displayed on the display portion 7103, and the light-emittingdevice can be used for the display portion 7103. In addition, here, thehousing 7101 is supported by a stand 7105.

Operation of the television set 7100 can be performed with an operationswitch of the housing 7101 or a separate remote controller 7110. Withoperation keys 7109 of the remote controller 7110, channels and volumecan be controlled and images displayed on the display portion 7103 canbe controlled. Furthermore, the remote controller 7110 may be providedwith a display portion 7107 for displaying data output from the remotecontroller 7110.

Note that the television set 7100 is provided with a receiver, a modem,and the like. With the receiver, a general television broadcast can bereceived. Furthermore, when the television set 7100 is connected to acommunication network by wired or wireless connection via the modem,one-way (from a transmitter to a receiver) or two-way (between atransmitter and a receiver, between receivers, or the like) datacommunication can be performed.

FIG. 6B illustrates a computer having a main body 7201, a housing 7202,a display portion 7203, a keyboard 7204, an external connection port7205, a pointing device 7206, and the like. Note that this computer ismanufactured using the light-emitting device for the display portion7203.

FIG. 6C illustrates a portable game machine having two housings, ahousing 7301 and a housing 7302, which are connected with a jointportion 7303 so that the portable game machine can be opened or folded.A display portion 7304 is incorporated in the housing 7301, and adisplay portion 7305 is incorporated in the housing 7302. In addition,the portable game machine illustrated in FIG. 6C includes a speakerportion 7306, a recording medium insertion portion 7307, an LED lamp7308, input means (an operation key 7309, a connection terminal 7310, asensor 7311 (a sensor having a function of measuring force,displacement, position, speed, acceleration, angular velocity,rotational frequency, distance, light, liquid, magnetism, temperature,chemical substance, sound, time, hardness, electric field, current,voltage, electric power, radiation, flow rate, humidity, gradient,oscillation, odor, or infrared rays), and a microphone 7312), and thelike. Needless to say, the structure of the portable game machine is notlimited to the above as long as the light-emitting device is used for atleast one of the display portion 7304 and the display portion 7305, andmay include other accessories as appropriate. The portable game machineillustrated in FIG. 6C has a function of reading out a program or datastored in a storage medium to display it on the display portion, and afunction of sharing information with another portable game machine bywireless communication. The functions of the portable game machineillustrated in FIG. 6C are not limited to these, and the portable gamemachine can have a variety of functions.

FIG. 6D illustrates an example of a mobile phone. A mobile phone 7400 isprovided with a display portion 7402 incorporated in a housing 7401,operation buttons 7403, an external connection port 7404, a speaker7405, a microphone 7406, and the like. Note that the mobile phone 7400is manufactured using the light-emitting device for the display portion7402.

When the display portion 7402 of the mobile phone 7400 illustrated inFIG. 6D is touched with a finger or the like, data can be input to themobile phone 7400. Further, operations such as making a call andcomposing an e-mail can be performed by touching the display portion7402 with a finger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying images. The secondmode is an input mode mainly for inputting data such as text. The thirdmode is a display-and-input mode in which two modes of the display modeand the input mode are combined.

For example, in the case of making a call or composing an e-mail, a textinput mode mainly for inputting text is selected for the display portion7402 so that text displayed on the screen can be input. In this case, itis preferable to display a keyboard or number buttons on almost theentire screen of the display portion 7402.

When a detection device including a sensor for detecting inclination,such as a gyroscope or an acceleration sensor, is provided inside themobile phone 7400, display on the screen of the display portion 7402 canbe automatically switched by determining the orientation of the mobilephone 7400 (whether the mobile phone is placed horizontally orvertically for a landscape mode or a portrait mode).

The screen modes are switched by touching the display portion 7402 oroperating the operation buttons 7403 of the housing 7401. The screenmodes can also be switched depending on the kind of image displayed onthe display portion 7402. For example, when a signal of an imagedisplayed on the display portion is a signal of moving image data, thescreen mode is switched to the display mode. When the signal is a signalof text data, the screen mode is switched to the input mode.

Moreover, in the input mode, when input by touching the display portion7402 is not performed for a certain period while a signal detected by anoptical sensor in the display portion 7402 is detected, the screen modemay be controlled so as to be switched from the input mode to thedisplay mode.

The display portion 7402 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken when thedisplay portion 7402 is touched with the palm or the finger, wherebypersonal authentication can be performed. Further, by providing abacklight or a sensing light source which emits near-infrared light inthe display portion, an image of a finger vein, a palm vein, or the likecan be taken.

FIGS. 7A and 7B illustrate a foldable tablet terminal. The tabletterminal is opened in FIG. 7A. The tablet terminal includes a housing9630, a display portion 9631 a, a display portion 9631 b, a display modeswitch 9034, a power switch 9035, a power saver switch 9036, a clasp9033, and an operation switch 9038. The tablet terminal is manufacturedusing the light-emitting device for either the display portion 9631 a orthe display portion 9631 b or both.

Part of the display portion 9631 a can be a touch panel region 9632 aand data can be input when a displayed operation key 9637 is touched.Although a structure in which a half region in the display portion 9631a has only a display function and the other half region also has a touchpanel function is shown as an example, the display portion 9631 a is notlimited to the structure. The whole region in the display portion 9631 amay have a touch panel function. For example, the display portion 9631 acan display keyboard buttons in the whole region to be a touch panel,and the display portion 9631 b can be used as a display screen.

As in the display portion 9631 a, part of the display portion 9631 b canbe a touch panel region 9632 b. When a keyboard display switching button9639 displayed on the touch panel is touched with a finger, a stylus, orthe like, a keyboard can be displayed on the display portion 9631 b.

Touch input can be performed in the touch panel region 9632 a and thetouch panel region 9632 b at the same time.

The display mode switch 9034 can switch the display between portraitmode, landscape mode, and the like, and between monochrome display andcolor display, for example. The power saver switch 9036 can controldisplay luminance in accordance with the amount of external light in useof the tablet terminal detected by an optical sensor incorporated in thetablet terminal. In addition to the optical sensor, another detectiondevice including a sensor for detecting inclination, such as a gyroscopeor an acceleration sensor, may be incorporated in the tablet terminal.

Note that FIG. 7A shows an example in which the display portion 9631 aand the display portion 9631 b have the same display area; however,without limitation thereon, one of the display portions may be differentfrom the other display portion in size and display quality. For example,higher definition images may be displayed on one of the display portions9631 a and 9631 b.

The tablet terminal is closed in FIG. 7B. The tablet terminal includesthe housing 9630, a solar cell 9633, a charge and discharge controlcircuit 9634, a battery 9635, and a DCDC converter 9636. In FIG. 7B, astructure including the battery 9635 and the DCDC converter 9636 isillustrated as an example of the charge and discharge control circuit9634.

Since the tablet terminal is foldable, the housing 9630 can be closedwhen the tablet terminal is not used. As a result, the display portion9631 a and the display portion 9631 b can be protected; thus, a tabletterminal which has excellent durability and excellent reliability interms of long-term use can be provided.

In addition, the tablet terminal illustrated in FIGS. 7A and 7B can havea function of displaying a variety of kinds of data (e.g., a stillimage, a moving image, and a text image), a function of displaying acalendar, a date, the time, or the like on the display portion, atouch-input function of operating or editing the data displayed on thedisplay portion by touch input, a function of controlling processing bya variety of kinds of software (programs), and the like.

The solar cell 9633 provided on a surface of the tablet terminal cansupply power to the touch panel, the display portion, a video signalprocessing portion, or the like. Note that the solar cell 9633 can beprovided on one or both surfaces of the housing 9630 to charge thebattery 9635 supplying power, which is preferable. The use of a lithiumion battery as the battery 9635 is advantageous in downsizing or thelike.

The structure and the operation of the charge and discharge controlcircuit 9634 illustrated in FIG. 7B will be described with reference toa block diagram in FIG. 7C. The solar cell 9633, the battery 9635, theDCDC converter 9636, a converter 9638, switches SW1 to SW3, and thedisplay portion 9631 are illustrated in FIG. 7C, and the battery 9635,the DCDC converter 9636, the converter 9638, and the switches SW1 to SW3correspond to the charge and discharge control circuit 9634 illustratedin FIG. 7B.

First, an example of the operation in the case where power is generatedby the solar cell 9633 using external light is described. The voltage ofpower generated by the solar cell 9633 is stepped up or down by the DCDCconverter 9636 so that the power has a voltage for charging the battery9635. Then, when the power from the solar cell 9633 is used for theoperation of the display portion 9631, the switch SW1 is turned on andthe voltage of the power is stepped up or down by the converter 9638 soas to be a voltage needed for the display portion 9631. In addition,when display on the display portion 9631 is not performed, the switchSW1 is turned off and the switch SW2 is turned on so that the battery9635 may be charged.

Note that the solar cell 9633 is described as an example of a powergeneration means; however, without limitation thereon, the battery 9635may be charged using another power generation means such as apiezoelectric element or a thermoelectric conversion element (Peltierelement). For example, the battery 9635 may be charged with anon-contact power transmission module which is capable of charging bytransmitting and receiving power by wireless (without contact), oranother charge means used in combination.

It is needless to say that one embodiment of the present invention isnot limited to the electronic device illustrated in FIGS. 7A to 7C aslong as the display portion described in this embodiment is included.

As described above, the electronic devices can be obtained byapplication of the light-emitting device that is one embodiment of thepresent invention. The light-emitting device has a remarkably wideapplication range, and can be applied to electronic devices in a varietyof fields.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments.

Embodiment 8

In this embodiment, examples of a lighting device to which alight-emitting device including the organometallic complex that is oneembodiment of the present invention is applied are described withreference to FIG. 8.

FIG. 8 illustrates an example in which the light-emitting device is usedas an indoor lighting device 8001. Since the light-emitting device canhave a large area, it can be used for a lighting device having a largearea. In addition, a lighting device 8002 in which a light-emittingregion has a curved surface can also be obtained with the use of ahousing with a curved surface. A light-emitting element included in thelight-emitting device described in this embodiment is in a thin filmform, which allows the housing to be designed more freely. Therefore,the lighting device can be elaborately designed in a variety of ways.Further, a wall of the room may be provided with a large-sized lightingdevice 8003.

Moreover, when the light-emitting device is used for a table by beingused as a surface of a table, a lighting device 8004 which has afunction as a table can be obtained. When the light-emitting device isused as part of other furniture, a lighting device which has a functionas the furniture can be obtained.

In this manner, a variety of lighting devices to which thelight-emitting device is applied can be obtained. Note that suchlighting devices are also embodiments of the present invention.

Note that the structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments.

Example 1 Synthesis Example 1

In this example, a synthesis method ofbis{4,6-dimethyl-2[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-P)₂(dibm)]), the organometallic complex whichis one embodiment of the present invention represented by StructuralFormula (100) in Embodiment 1, is described. The structure of[Ir(dmdppr-P)₂(dibm)] (abbreviation) is shown below.

Step 1: Synthesis of 2,3-Bis(3,5-dimethylphenyl)pyrazine (abbreviation:Hdmdppr)

First, 5.00 g of 2,3-dichloropyrazine, 10.23 g of3,5-dimethylphenylboronic acid, 7.19 g of sodium carbonate, 0.29 g ofbis(triphenylphosphine)palladium(II) dichloride (Pd(PPh₃)₂Cl₂), 20 mL ofwater, and 20 mL of acetonitrile were put into a recovery flask equippedwith a reflux pipe, and the air in the flask was replaced with argon.This reaction container was subjected to irradiation with microwaves(2.45 GHz, 100 W) for 60 minutes to be heated. Here, into the flask werefurther put 2.55 g of 3,5-dimethylphenylboronic acid, 1.80 g of sodiumcarbonate, 0.070 g of Pd(PPh₃)₂Cl₂, 5 mL of water, and 5 mL ofacetonitrile, and irradiation with microwaves (2.45 GHz, 100 W) wasperformed again for 60 minutes so that heating was performed.

Then, water was added to this solution and the organic layer wasextracted with dichloromethane. The obtained organic layer was washedwith a saturated aqueous solution of sodium hydrogen carbonate, water,and saturated brine, and was dried with magnesium sulfate. After thedrying, the solution was filtered. The solvent of this solution wasdistilled off, and the obtained residue was purified by flash columnchromatography using hexane and ethyl acetate as a developing solvent ina volume ratio of 5:1. The solvent was distilled off, and the obtainedsolid was purified by flash column chromatography using dichloromethaneand ethyl acetate as a developing solvent in a volume ratio of 10:1, sothat Hdmdppr (abbreviation), which was the pyrazine derivative to beproduced, was obtained as a white powder in a yield of 44%. Note thatthe irradiation with microwaves was performed using a microwavesynthesis system (Discover, manufactured by CEM Corporation). Asynthesis scheme of Step 1 is shown in (a-1).

Step 2: Synthesis of 2,3-Bis(3,5-dimethylphenyl)-5-phenylpyrazine(abbreviation: Hdmdppr-P)

First, 4.28 g of Hdmdppr (abbreviation) obtained in Step 1 and 80 mL ofdry THF were put into a three-neck flask and the air in the flask wasreplaced with nitrogen. After the flask was cooled with ice, 9.5 mL ofphenyl lithium (1.9M solution of phenyl lithium in butyl ether) wasadded dropwise, and the mixture was stirred at room temperature for 23.5hours. The reacted solution was poured into water and the solution wassubjected to extraction with chloroform. The obtained organic layer waswashed with water and saturated brine, and dried with magnesium sulfate.Manganese oxide was added to the obtained mixture and the mixture wasstirred for 30 minutes. Then, the solution was filtered and the solventwas distilled off. The obtained residue was purified by silica gelcolumn chromatography using dichloromethane as a developing solvent, sothat Hdmdppr-P (abbreviation), which was the pyrazine derivative to beproduced, was obtained as an orange oil in a yield of 26%. A synthesisscheme of Step 2 is shown in (a-2).

Step 3: Synthesis ofDi-μ-chloro-tetrakis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}diiridium(III)(abbreviation: [Ir(dmdppr-P)₂Cl]₂)

Next, into a recovery flask equipped with a reflux pipe were put 15 mLof 2-ethoxyethanol, 5 mL of water, 1.40 g of Hdmdppr-P (abbreviation)obtained in Step 2, and 0.51 g of iridium chloride hydrate (IrCl₃.H₂O)(produced by Sigma-Aldrich Corporation), and the air in the flask wasreplaced with argon. After that, irradiation with microwaves (2.45 GHz,100 W) was performed for 1 hour to cause a reaction. The solvent wasdistilled off, and then the obtained residue was suction-filtered andwashed with ethanol to give [Ir(dmdppr-P)₂Cl]₂ (abbreviation) that is adinuclear complex as a reddish brown powder in a yield of 58%. Asynthesis scheme of Step 3 is shown in (a-3).

Step 4: Synthesis ofBis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-P)₂(dibm)])

Further, into a recovery flask equipped with a reflux pipe were put 30mL of 2-ethoxyethanol, 0.94 g of [Ir(dmdppr-P)₂Cl]₂ that is thedinuclear complex obtained in Step 3, 0.23 g of diisobutyrylmethane(abbreviation: Hdibm), and 0.52 g of sodium carbonate, and the air inthe flask was replaced with argon. After that, heating was performed byirradiation with microwaves (2.45 GHz, 120 W) for 60 minutes. Thesolvent was distilled off, and the obtained residue was suction-filteredwith ethanol. The obtained solid was washed with water and ethanol andrecrystallization was carried out with a mixed solvent ofdichloromethane and ethanol, so that [Ir(dmdppr-P)₂(dibm)](abbreviation), the organometallic complex that is one embodiment of thepresent invention, was obtained as a dark red powder in a yield of 75%.A synthesis scheme of Step 4 is shown in (a-4).

An analysis result by nuclear magnetic resonance (¹H-NMR) spectroscopyof the dark red powder obtained by the above-described synthesis methodis described below. FIG. 9 shows the ¹H-NMR chart. These resultsrevealed that [Ir(dmdppr-P)₂(dibm)] (abbreviation), the organometalliccomplex which is one embodiment of the present invention represented byStructural Formula (100), was obtained in Synthesis Example 1.

¹H-NMR. δ(CDCl₃): 0.79 (d, 6H), 0.96 (d, 6H), 1.41 (s, 6H), 1.96 (s,6H), 2.24-2.28 (m, 2H), 2.41 (s, 12H), 5.08 (s, 1H), 6.46 (s, 2H), 6.82(s, 2H), 7.18 (s, 2H), 7.39-7.50 (m, 10H), 8.03 (d, 4H), 8.76 (s, 2H).

Next, an ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as an “absorption spectrum”) of a dichloromethane solutionof [Ir(dmdppr-P)₂(dibm)] (abbreviation) and an emission spectrum thereofwere measured. The measurement of the absorption spectrum was conductedat room temperature, for which an ultraviolet-visible lightspectrophotometer (V550 type manufactured by Japan SpectroscopyCorporation) was used and the dichloromethane solution (0.062 mmol/L)was put in a quartz cell. In addition, the measurement of the emissionspectrum was conducted at room temperature, for which a fluorescencespectrophotometer (FS920 manufactured by Hamamatsu Photonics K. K.) wasused and the degassed dichloromethane solution (0.010 mmol/L) was put ina quartz cell. Measurement results of the obtained absorption andemission spectra are shown in FIG. 10, in which the horizontal axisrepresents wavelength and the vertical axes represent absorptionintensity and emission intensity. In FIG. 10 where there are two solidlines, the thin line represents the absorption spectrum and the thickline represents the emission spectrum. Note that the absorption spectrumin FIG. 10 is the results obtained in such a way that the absorptionspectrum measured by putting only dichloromethane in a quartz cell wassubtracted from the absorption spectrum measured by putting thedichloromethane solution (0.062 mmol/L) in a quartz cell.

As shown in FIG. 10, [Ir(dmdppr-P)₂(dibm)] (abbreviation), theorganometallic complex that is one embodiment of the present invention,has an emission peak at around 640 nm, and reddish orange light emissionwas observed from the dichloromethane solution.

Further, weight loss percentage of [Ir(dmdppr-P)₂(dibm)] (abbreviation)was measured by a high vacuum differential type differential thermalbalance (TG/DTA 2410SA, manufactured by Bruker AXS K.K.). Thetemperature was increased at a rate of 10° C./min under a degree ofvacuum of 1×10⁻³ Pa. As a result, the weight loss percentage of[Ir(dmdppr-P)₂(dibm)] (abbreviation), the organometallic complex that isone embodiment of the present invention, was found to be 100% as shownin FIG. 37, which indicated a favorable sublimation property of theorganometallic complex. As a comparative example, the weight losspercentage of Compound A in which methyl groups are not bonded to the3-position and the 5-position is shown. A comparison with a weight losspercentage of 78% of Compound A revealed that the organometallic complexthat is one embodiment of the present invention has an improvedsublimation property by having the methyl groups at the 3-position andthe 5-position.

Example 2 Synthesis Example 2

In this example, a synthesis method ofbis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III) (abbreviation:[Ir(dmdppm)₂(dibm)]), the organometallic complex which is one embodimentof the present invention represented by Structural Formula (107) inEmbodiment 1, is described. The structure of [Ir(dmdppm)₂(dibm)](abbreviation) is shown below.

Step 1: Synthesis of 4,6-Bis(3,5-dimethylphenyl)pyrimidine(abbreviation: Hdmdppm)

First, 5.97 g of 4,6-dichloropyrimidine, 12.04 g of3,5-dimethylphenylboronic acid, 8.48 g of sodium carbonate, 0.34 g ofbis(triphenylphosphine)palladium(II) dichloride (Pd(PPh₃)₂Cl₂), 20 mL ofwater, and 20 mL of 1,3-dimethyl-3,4, 5,6-tetrahydro-2(1H)pyrimidinone(abbreviation: DMPU) were put into a recovery flask equipped with areflux pipe, and the air in the flask was replaced with argon. Thisreaction container was subjected to irradiation with microwaves (2.45GHz, 100 W) for 60 minutes to be heated. Here, into the flask werefurther put 2.58 g of 3,5-dimethylphenylboronic acid, 1.78 g of sodiumcarbonate, 0.070 g of Pd(PPh₃)₂Cl₂, 5 mL of water, and 5 mL of DMPU, andirradiation with microwaves (2.45 GHz, 100 W) was performed again for 60minutes so that heating was performed.

After that, the obtained residue was suction-filtered with water andwashed with water and ethanol. The obtained solid was dissolved indichloromethane, filtered through a filter aid in which Celite, alumina,and Celite were stacked in that order, and then washed with ethanol, sothat Hdmdppm, which was the pyrimidine derivative to be produced, wasobtained as a white powder in a yield of 56%. Note that the irradiationwith microwaves was performed using a microwave synthesis system(Discover, manufactured by CEM Corporation). A synthesis scheme of Step1 is shown in (b-1).

Step 2: Synthesis ofDi-μ-chloro-tetrakis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}diiridium(III)(abbreviation: [Ir(dmdppm)₂Cl]₂)

Next, into a recovery flask equipped with a reflux pipe were put 15 mLof 2-ethoxyethanol, 5 mL of water, 2.10 g of Hdmdppm (abbreviation)obtained in Step 1, and 1.07 g of iridium chloride hydrate (IrCl₃.H₂O)(produced by Sigma-Aldrich Corporation), and the air in the flask wasreplaced with argon. After that, irradiation with microwaves (2.45 GHz,100 W) was performed for 1 hour to cause a reaction. The solvent wasdistilled off, and then the obtained residue was suction-filtered andwashed with ethanol to give [Ir(dmdppm)₂Cl]₂ (abbreviation) that is adinuclear complex as a reddish brown powder in a yield of 74%. Asynthesis scheme of Step 2 is shown in (b-2).

Step 3: Synthesis ofBis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppm)₂(dibm)])

Further, into a recovery flask equipped with a reflux pipe were put 30mL of 2-ethoxyethanol, 1.09 g of [Ir(dmdppm)₂Cl]₂ (abbreviation) that isthe dinuclear complex obtained in Step 2, 0.32 g of diisobutyrylmethane(abbreviation: Hdibm), and 0.72 g of sodium carbonate, and the air inthe flask was replaced with argon. After that, heating was performed byirradiation with microwaves (2.45 GHz, 120 W) for 60 minutes. Thesolvent was distilled off, and the obtained residue was suction-filteredwith ethanol. The obtained solid was washed with water and ethanol andrecrystallization was carried out with a mixed solvent ofdichloromethane and ethanol, so that [Ir(dmdppm)₂(dibm)] (abbreviation),the organometallic complex that is one embodiment of the presentinvention, was obtained as a red powder in a yield of 62%. A synthesisscheme of Step 3 is shown in (b-3).

An analysis result by nuclear magnetic resonance (¹H-NMR) spectroscopyof the red powder obtained by the above-described synthesis method isdescribed below. FIG. 11 shows the ¹H-NMR chart. These results revealedthat [Ir(dmdppm)₂(dibm)] (abbreviation), the organometallic complexwhich is one embodiment of the present invention represented byStructural Formula (107), was obtained in Synthesis Example 2.

¹H-NMR. δ(CDCl₃): 0.69 (d, 6H), 0.82 (d, 6H), 1.51 (s, 6H), 2.17-2.23(m, 2H), 2.31 (s, 6H), 2.45 (s, 12H), 5.19 (s, 1H), 6.61 (s, 2H), 7.17(s, 2H), 7.56 (s, 2H), 7.82 (s, 4H), 8.11 (d, 2H), 8.88 (d, 2H).

Next, an ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as an “absorption spectrum”) of a dichloromethane solutionof [Ir(dmdppm)₂(dibm)] (abbreviation) and an emission spectrum thereofwere measured. The measurement of the absorption spectrum was conductedat room temperature, for which an ultraviolet-visible lightspectrophotometer (V550 type manufactured by Japan SpectroscopyCorporation) was used and the dichloromethane solution (0.072 mmol/L)was put in a quartz cell. In addition, the measurement of the emissionspectrum was conducted at room temperature, for which a fluorescencespectrophotometer (FS920 manufactured by Hamamatsu Photonics K. K.) wasused and the degassed dichloromethane solution (0.072 mmol/L) was put ina quartz cell. Measurement results of the obtained absorption andemission spectra are shown in FIG. 12, in which the horizontal axisrepresents wavelength and the vertical axes represent absorptionintensity and emission intensity. In FIG. 12 where there are two solidlines, the thin line represents the absorption spectrum and the thickline represents the emission spectrum. Note that the absorption spectrumin FIG. 12 is the results obtained in such a way that the absorptionspectrum measured by putting only dichloromethane in a quartz cell wassubtracted from the absorption spectrum measured by putting thedichloromethane solution (0.072 mmol/L) in a quartz cell.

As shown in FIG. 12, [Ir(dmdppm)₂(dibm)] (abbreviation), theorganometallic complex that is one embodiment of the present invention,has an emission peak at around 609 nm, and reddish orange light emissionwas observed from the dichloromethane solution.

Example 3 Synthesis Example 3

In this example, a synthesis method ofbis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}(2,2′,6,6′-tetramethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppm)₂(dpm)]), the organometallic complex which isone embodiment of the present invention represented by StructuralFormula (108) in Embodiment 1, is described. The structure of[Ir(dmdppm)₂(dpm)] (abbreviation) is shown below.

Step 1: Synthesis of 4,6-Bis(3,5-dimethylphenyl)pyrimidine(abbreviation: Hdmdppm)

First, 5.97 g of 4,6-dichloropyrimidine, 12.04 g of3,5-dimethylphenylboronic acid, 8.48 g of sodium carbonate, 0.34 g ofbis(triphenylphosphine)palladium(II) dichloride (Pd(PPh₃)₂Cl₂), 20 mL ofwater, and 20 mL of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)pyrimidinone(abbreviation: DMPU) were put into a recovery flask equipped with areflux pipe, and the air in the flask was replaced with argon. Thisreaction container was subjected to irradiation with microwaves (2.45GHz, 100 W) for 60 minutes to be heated. Here, into the flask werefurther put 2.58 g of 3,5-dimethylphenylboronic acid, 1.78 g of sodiumcarbonate, 0.070 g of Pd(PPh₃)₂Cl₂, 5 mL of water, and 5 mL of DMPU, andirradiation with microwaves (2.45 GHz, 100 W) was performed again for 60minutes so that heating was performed.

After that, the obtained residue was suction-filtered with water andwashed with water and ethanol. The obtained solid was dissolved indichloromethane, filtered through a filter aid in which Celite, alumina,and Celite were stacked in that order, and then washed with ethanol, sothat Hdmdppm (abbreviation), which was the pyrimidine derivative to beproduced, was obtained as a white powder in a yield of 56%. Note thatthe irradiation with microwaves was performed using a microwavesynthesis system (Discover, manufactured by CEM Corporation). Asynthesis scheme of Step 1 is shown in (c-1).

Step 2: Synthesis ofDi-μ-chloro-tetrakis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}diiridium(III) (abbreviation: [Ir(dmdppm)₂Cl]₂)

Next, into a recovery flask equipped with a reflux pipe were put 15 mLof 2-ethoxyethanol, 5 mL of water, 2.10 g of Hdmdppm (abbreviation)obtained in Step 1, and 1.07 g of iridium chloride hydrate (IrCl₃.H₂O)(produced by Sigma-Aldrich Corporation), and the air in the flask wasreplaced with argon. After that, irradiation with microwaves (2.45 GHz,100 W) was performed for 1 hour to cause a reaction. The solvent wasdistilled off, and then the obtained residue was suction-filtered andwashed with ethanol to give [Ir(dmdppm)₂Cl]₂ (abbreviation) that is adinuclear complex as a reddish brown powder in a yield of 74%. Asynthesis scheme of Step 2 is shown in (c-2).

Step 3: Synthesis ofBis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}(2,2′,6,6′-tetramethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppm)₂(dpm)])

Further, into a recovery flask equipped with a reflux pipe were put 30mL of 2-ethoxyethanol, 1.08 g of [Ir(dmdppm)₂Cl]₂ (abbreviation) that isthe dinuclear complex obtained in Step 2, 0.37 g of dipivaloylmethane(abbreviation: Hdpm), and 0.71 g of sodium carbonate, and the air in theflask was replaced with argon. After that, heating was performed byirradiation with microwaves (2.45 GHz, 120 W) for 60 minutes. Thesolvent was distilled off, and the obtained residue was suction-filteredwith ethanol. The obtained solid was washed with water and ethanol. Theobtained solid was dissolved in dichloromethane and filtered through afilter aid in which Celite, alumina, and Celite were stacked in thatorder. Then, recrystallization was carried out with a mixed solvent ofdichloromethane and ethanol; thus, [Ir(dmdppm)₂(dpm)] (abbreviation),the organometallic complex that is one embodiment of the presentinvention, was obtained as a red powder in a yield of 21%. A synthesisscheme of Step 3 is shown in (c-3).

An analysis result by nuclear magnetic resonance (¹H-NMR) spectroscopyof the red powder obtained by the above-described synthesis method isdescribed below. FIG. 13 shows the ¹H-NMR chart. These results revealedthat [Ir(dmdppm)₂(dpm)] (abbreviation), the organometallic complex whichis one embodiment of the present invention represented by StructuralFormula (108), was obtained in Synthesis Example 3.

¹H-NMR. δ(CDCl₃): 0.84 (s, 18H), 1.51 (s, 6H), 2.31 (s, 6H), 2.45 (s,12H), 5.52 (s, 1H), 6.60 (s, 2H), 7.17 (s, 2H), 7.55 (s, 2H), 7.81 (s,4H), 8.10 (s, 2H), 8.84 (d, 2H).

Next, an ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as an “absorption spectrum”) of a dichloromethane solutionof [Ir(dmdppm)₂(dpm)] (abbreviation) and an emission spectrum thereofwere measured. The measurement of the absorption spectrum was conductedat room temperature, for which an ultraviolet-visible lightspectrophotometer (V550 type manufactured by Japan SpectroscopyCorporation) was used and the dichloromethane solution (0.070 mmol/L)was put in a quartz cell. In addition, the measurement of the emissionspectrum was conducted at room temperature, for which a fluorescencespectrophotometer (FS920 manufactured by Hamamatsu Photonics K. K.) wasused and the degassed dichloromethane solution (0.070 mmol/L) was put ina quartz cell. Measurement results of the obtained absorption andemission spectra are shown in FIG. 14, in which the horizontal axisrepresents wavelength and the vertical axes represent absorptionintensity and emission intensity. In FIG. 14 where there are two solidlines, the thin line represents the absorption spectrum and the thickline represents the emission spectrum. Note that the absorption spectrumin FIG. 14 is the results obtained in such a way that the absorptionspectrum measured by putting only dichloromethane in a quartz cell wassubtracted from the absorption spectrum measured by putting thedichloromethane solution (0.070 mmol/L) in a quartz cell.

As shown in FIG. 14, [Ir(dmdppm)₂(dpm)] (abbreviation), theorganometallic complex that is one embodiment of the present invention,has an emission peak at around 615 nm, and reddish orange light emissionwas observed from the dichloromethane solution.

Example 4

In this example, a light-emitting element 1 in which[Ir(dmdppr-P)₂(dibm)] (abbreviation), the organometallic complex whichis one embodiment of the present invention represented by StructuralFormula (100), is used for a light-emitting layer is described withreference to FIG. 15. Chemical formulae of materials used in thisexample are shown below.

<<Fabrication of Light-Emitting Element 1>>

First, indium tin oxide containing silicon oxide (ITSO) was depositedover a glass substrate 1100 by a sputtering method, so that a firstelectrode 1101 which functions as an anode was formed. The thickness was110 nm and the electrode area was 2 mm×2 mm.

Then, as pretreatment for forming the light-emitting element over thesubstrate 1100, UV ozone treatment was performed for 370 seconds afterwashing of a surface of the substrate with water and baking that wasperformed at 200° C. for 1 hour.

After that, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to approximately 10⁻⁴ Pa,and was subjected to vacuum baking at 170° C. for 30 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate 1100 was cooled down for about 30 minutes.

Next, the substrate 1100 was fixed to a holder provided in the vacuumevaporation apparatus so that a surface of the substrate 1100 over whichthe first electrode 1101 was formed faced downward. In this example, acase will be described in which a hole-injection layer 1111, ahole-transport layer 1112, a light-emitting layer 1113, anelectron-transport layer 1114, and an electron-injection layer 1115which are included in an EL layer 1102 are sequentially formed by avacuum evaporation method.

After reducing the pressure of the vacuum evaporation apparatus to 10⁻⁴Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) andmolybdenum(VI) oxide were co-evaporated with a mass ratio of DBT3P-II(abbreviation) to molybdenum oxide being 4:2, whereby the hole-injectionlayer 1111 was formed over the first electrode 1101. The thickness ofthe hole-injection layer 1111 was 40 nm. Note that the co-evaporation isan evaporation method in which some different substances are evaporatedfrom some different evaporation sources at the same time.

Then, 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:BPAFLP) was deposited by evaporation to a thickness of 20 nm, so thatthe hole-transport layer 1112 was formed.

Next, the light-emitting layer 1113 was formed over the hole-transportlayer 1112 in the following manner. Co-evaporated were2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II), 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(abbreviation: NPB), andbis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-P)₂(dibm)]) with a mass ratio of 2mDBTPDBq-II(abbreviation) to NPB (abbreviation) and [Ir(dmdppr-P)₂(dibm)](abbreviation) being 0.8:0.2:0.05. The thickness of the light-emittinglayer 1113 was 40 nm.

Then, over the light-emitting layer 1113, 2mDBTPDBq-II (abbreviation)was deposited by evaporation to a thickness of 10 nm and thenbathophenanthroline (abbreviation: BPhen) was deposited by evaporationto a thickness of 20 nm, whereby the electron-transport layer 1114having a stacked structure was formed. Furthermore, lithium fluoride wasdeposited by evaporation to a thickness of 1 nm over theelectron-transport layer 1114, whereby the electron-injection layer 1115was formed.

Finally, aluminum was deposited by evaporation to a thickness of 200 nmover the electron-injection layer 1115 to form a second electrode 1103serving as a cathode; thus, the light-emitting element 1 was obtained.Note that in all the above evaporation steps, evaporation was performedby a resistance-heating method.

An element structure of the light-emitting element 1 obtained asdescribed above is shown in Table 1.

TABLE 1 Hole- Light- Electron- First Hole-injection transport emittingElectron- injection Second Electrode Layer Layer Layer transport LayerLayer Electrode Light-emitting ITSO DBT3P-II:MoO_(x) BPAFLP * ** BPhenLiF Al Element 1 (110 nm) (4:2 40 nm) (20 nm) (20 nm) (1 nm) (200 nm) *2mDBTPDBq-II:NPB:[Ir(dmdppr-P)₂(dibm)] (0.8:0.2:0.05 40 nm) **2mDBTPDBq-II (10 nm)

Further, the fabricated light-emitting element 1 was sealed in a glovebox containing a nitrogen atmosphere so as not to be exposed to the air(specifically, a sealant was applied onto an outer edge of the elementand heat treatment was performed at 80° C. for 1 hour at the time ofsealing).

<<Operation Characteristics of Light-Emitting Element 1>>

Operation characteristics of the fabricated light-emitting element 1were measured. Note that the measurement was carried out at roomtemperature (under an atmosphere in which the temperature was kept at25° C.).

FIG. 16 shows current density-luminance characteristics of thelight-emitting element 1. In FIG. 16, the vertical axis representsluminance (cd/m²) and the horizontal axis represents current density(mA/cm²). FIG. 17 shows voltage-luminance characteristics of thelight-emitting element 1. In FIG. 17, the vertical axis representsluminance (cd/m²) and the horizontal axis represents voltage (V).Further, FIG. 18 shows luminance-current efficiency characteristics ofthe light-emitting element 1. In FIG. 18, the vertical axis representscurrent efficiency (cd/A) and the horizontal axis represents luminance(cd/m²). FIG. 19 shows voltage-current characteristics of thelight-emitting element 1. In FIG. 19, the vertical axis representscurrent (mA) and the horizontal axis represents voltage (V).

FIG. 18 reveals high efficiency of the light-emitting element 1 in whichpart of the light-emitting layer uses [Ir(dmdppr-P)₂(dibm)](abbreviation), the organometallic complex that is one embodiment of thepresent invention. Table 2 shows initial values of main characteristicsof the light-emitting element 1 at a luminance of about 1000 cd/m².

TABLE 2 Current Current Power Quantum Voltage Current DensityChromaticity Luminance Efficiency Efficiency Efficiency (V) (mA)(mA/cm²) (x, y) (cd/m²) (cd/A) (lm/W) (%) Light- 3.3 0.22 5.6 (0.69,0.31) 920 16.0 16.0 26.0 emitting Element 1

The above results show that the light-emitting element 1 fabricated inthis example is a high-luminance light-emitting element having highcurrent efficiency. Moreover, as for color purity, it can be found thatthe light-emitting element exhibits red light emission with excellentcolor purity.

FIG. 20 shows an emission spectrum when a current at a current densityof 2.5 mA/cm² was supplied to the light-emitting element 1. As shown inFIG. 20, the emission spectrum of the light-emitting element 1 has apeak at around 640 nm and it is indicated that the peak is derived fromemission of the organometallic complex [Ir(dmdppr-P)₂(dibm)](abbreviation). Note that FIG. 20 also shows an emission spectrum of acomparative light-emitting element 1 as a comparative example. Thecomparative light-emitting element 1 was fabricated using anorganometallic complex [Ir(tppr)₂(dpm)] (abbreviation) instead of theorganometallic complex [Ir(dmdppr-P)₂(dibm)] (abbreviation) which wasused in the light-emitting element 1. Thus, it was observed that halfwidth of the emission spectrum of the light-emitting element 1 issmaller than that in the emission spectrum of the comparativelight-emitting element 1. This can be presumed to be an effect broughtabout by the structure of the organometallic complex[Ir(dmdppr-P)₂(dibm)] (abbreviation), in which methyl groups are bondedto the 2-position and the 4-position of the phenyl group bonded toiridium. Therefore, it can be said that the light-emitting element 1 hashigh emission efficiency and achieves high color purity.

The light-emitting element 1 was subjected to reliability tests. Resultsof the reliability tests are shown in FIG. 21 and FIG. 22. In FIG. 21,the vertical axis represents normalized luminance (%) with an initialluminance of 100% and the horizontal axis represents driving time (h) ofthe element. Note that in one of the reliability tests, thelight-emitting element 1 was driven under the conditions where theinitial luminance was set to 5000 cd/m² and the current density wasconstant. The light-emitting element 1 kept about 68% of the initialluminance after 100 hours elapsed. Further, in FIG. 22, the verticalaxis represents normalized luminance (%) with an initial luminance of100% and the horizontal axis represents driving time (h) of the element.Note that in the other of the reliability tests, the light-emittingelement 1 was driven with a current value of 0.3 mA. The light-emittingelement 1 kept about 90% of the initial luminance after 100 hourselapsed.

Thus, both of the reliability tests which were conducted under differentconditions showed that the light-emitting element 1 is highly reliable.In addition, it was confirmed that with the use of the organometalliccomplex that is one embodiment of the present invention, alight-emitting element with a long lifetime can be obtained.

Example 5

In this example, a light-emitting element 2 in which [Ir(dmdppm)₂(dibm)](abbreviation), the organometallic complex which is one embodiment ofthe present invention represented by Structural Formula (107), is usedfor a light-emitting layer is described. Note that in the description ofthe light-emitting element 2 in this example, FIG. 15 which is used inthe description of the light-emitting element 1 in Example 4 is to bereferred to. Chemical formulae of materials used in this example areshown below.

<<Fabrication of Light-Emitting Element 2>>

First, indium tin oxide containing silicon oxide (ITSO) was depositedover the glass substrate 1100 by a sputtering method, so that the firstelectrode 1101 which functions as an anode was formed. The thickness was110 nm and the electrode area was 2 mm×2 mm.

Then, as pretreatment for forming the light-emitting element over thesubstrate 1100, UV ozone treatment was performed for 370 seconds afterwashing of a surface of the substrate with water and baking that wasperformed at 200° C. for 1 hour.

After that, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to approximately 10⁻⁴ Pa,and was subjected to vacuum baking at 170° C. for 30 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate 1100 was cooled down for about 30 minutes.

Next, the substrate 1100 was fixed to a holder provided in the vacuumevaporation apparatus so that a surface of the substrate 1100 over whichthe first electrode 1101 was formed faced downward. In this example, acase will be described in which the hole-injection layer 1111, thehole-transport layer 1112, the light-emitting layer 1113, theelectron-transport layer 1114, and the electron-injection layer 1115which are included in the EL layer 1102 are sequentially formed by avacuum evaporation method.

After reducing the pressure of the vacuum evaporation apparatus to 10⁻⁴Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) andmolybdenum(VI) oxide were co-evaporated with a mass ratio of DBT3P-II(abbreviation) to molybdenum oxide being 4:2, whereby the hole-injectionlayer 1111 was formed over the first electrode 1101. The thickness ofthe hole-injection layer 1111 was 40 nm. Note that the co-evaporation isan evaporation method in which some different substances are evaporatedfrom some different evaporation sources at the same time.

Then, 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:BPAFLP) was deposited by evaporation to a thickness of 20 nm, so thatthe hole-transport layer 1112 was formed.

Next, the light-emitting layer 1113 was formed over the hole-transportlayer 1112 in the following manner. Co-evaporated were2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II), 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(abbreviation: NPB), andbis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppm)₂(dibm)]) with a mass ratio of 2mDBTPDBq-II(abbreviation) to NPB (abbreviation) and [Ir(dmdppm)₂(dibm)](abbreviation) being 0.8:0.2:0.05. The thickness of the light-emittinglayer 1113 was 40 nm.

Then, over the light-emitting layer 1113, 2mDBTPDBq-II (abbreviation)was deposited by evaporation to a thickness of 10 nm and thenbathophenanthroline (abbreviation: BPhen) was deposited by evaporationto a thickness of 20 nm, whereby the electron-transport layer 1114having a stacked structure was formed. Furthermore, lithium fluoride wasdeposited by evaporation to a thickness of 1 nm over theelectron-transport layer 1114, whereby the electron-injection layer 1115was formed.

Finally, aluminum was deposited by evaporation to a thickness of 200 nmover the electron-injection layer 1115 to form the second electrode 1103serving as a cathode; thus, the light-emitting element 2 was obtained.Note that in all the above evaporation steps, evaporation was performedby a resistance-heating method.

An element structure of the light-emitting element 2 obtained asdescribed above is shown in Table 3.

TABLE 3 Hole- Hole- Light- Electron- First injection transport emittingElectron-transport injection Second Electrode Layer Layer Layer LayerLayer Electrode Light- ITSO DBT3P-II:MoO_(x) BPAFLP * ** BPhen LiF Alemitting (110 nm) (4:2 40 nm) (20 nm) (20 nm) (1 nm) (200 nm) Element2 * 2mDBTPDBq-II:NPB:[Ir(dmdppm)₂(dibm)] (0.8:0.2:0.05 40 nm) **2mDBTPDBq-II (10 nm)

Further, the fabricated light-emitting element 2 was sealed in a glovebox containing a nitrogen atmosphere so as not to be exposed to the air(specifically, a sealant was applied onto an outer edge of the elementand heat treatment was performed at 80° C. for 1 hour at the time ofsealing).

<<Operation Characteristics of Light-Emitting Element 2>>

Operation characteristics of the fabricated light-emitting element 2were measured. Note that the measurement was carried out at roomtemperature (under an atmosphere in which the temperature was kept at25° C.).

FIG. 23 shows current density-luminance characteristics of thelight-emitting element 2. In FIG. 23, the vertical axis representsluminance (cd/m²) and the horizontal axis represents current density(mA/cm²). FIG. 24 shows voltage-luminance characteristics of thelight-emitting element 2. In FIG. 24, the vertical axis representsluminance (cd/m²) and the horizontal axis represents voltage (V).Further, FIG. 25 shows luminance-current efficiency characteristics ofthe light-emitting element 2. In FIG. 25, the vertical axis representscurrent efficiency (cd/A) and the horizontal axis represents luminance(cd/m²). FIG. 26 shows voltage-current characteristics of thelight-emitting element 2. In FIG. 26, the vertical axis representscurrent (mA) and the horizontal axis represents voltage (V).

FIG. 25 reveals high efficiency of the light-emitting element 2 in whichpart of the light-emitting layer uses [Ir(dmdppm)₂(dibm)](abbreviation), the organometallic complex that is one embodiment of thepresent invention. Table 4 shows initial values of main characteristicsof the light-emitting element 2 at a luminance of about 1000 cd/m².

TABLE 4 Current Current Power Quantum Voltage Current DensityChromaticity Luminance Efficiency Efficiency Efficiency (V) (mA)(mA/cm²) (x, y) (cd/m²) (cd/A) (lm/W) (%) Light- 2.9 0.062 1.6 (0.62,0.38) 870 56 60 31 emitting Element 2

The above results show that the light-emitting element 2 fabricated inthis example is a high-luminance light-emitting element having highcurrent efficiency. Moreover, as for color purity, it can be found thatthe light-emitting element exhibits reddish orange light emission withexcellent color purity.

FIG. 27 shows an emission spectrum when a current at a current densityof 2.5 mA/cm² was supplied to the light-emitting element 2. As shown inFIG. 27, the emission spectrum of the light-emitting element 2 has apeak at around 610 nm and it is indicated that the peak is derived fromemission of the organometallic complex [Ir(dmdppm)₂(dibm)](abbreviation). Note that FIG. 27 also shows an emission spectrum of acomparative light-emitting element 2 as a comparative example. Thecomparative light-emitting element 2 was fabricated using anorganometallic complex [Ir(dppm)₂(acac)] (abbreviation) instead of theorganometallic complex [Ir(dmdppm)₂(dibm)] (abbreviation) which was usedin the light-emitting element 2. Thus, it was observed that half widthof the emission spectrum of the light-emitting element 2 is smaller thanthat in the emission spectrum of the comparative light-emitting element2. This can be presumed to be an effect brought about by the structureof the organometallic complex [Ir(dmdppm)₂(dibm)] (abbreviation), inwhich methyl groups are bonded to the 2-position and the 4-position ofthe phenyl group bonded to iridium. Therefore, it can be said that thelight-emitting element 2 has high emission efficiency and achieves highcolor purity.

The light-emitting element 2 was subjected to reliability tests. Resultsof the reliability tests are shown in FIG. 28 and FIG. 29. In FIG. 28,the vertical axis represents normalized luminance (%) with an initialluminance of 100% and the horizontal axis represents driving time (h) ofthe element. Note that in one of the reliability tests, thelight-emitting element 2 was driven under the conditions where theinitial luminance was set to 5000 cd/m² and the current density wasconstant. The light-emitting element 2 kept about 86% of the initialluminance after 100 hours elapsed. Further, in FIG. 29, the verticalaxis represents normalized luminance (%) with an initial luminance of100% and the horizontal axis represents driving time (h) of the element.Note that in the other of the reliability tests, the light-emittingelement 2 was driven with a current value of 0.3 mA. The light-emittingelement 2 kept about 90% of the initial luminance after 100 hourselapsed.

Thus, both of the reliability tests which were conducted under differentconditions showed that the light-emitting element 2 is highly reliable.In addition, it was confirmed that with the use of the organometalliccomplex that is one embodiment of the present invention, alight-emitting element with a long lifetime can be obtained.

Example 6

In this example, a light-emitting element 3 in which [Ir(dmdppm)₂(dpm)](abbreviation), the organometallic complex which is one embodiment ofthe present invention represented by Structural Formula (108), is usedfor a light-emitting layer is described. Note that in the description ofthe light-emitting element 3 in this example, FIG. 15 which is used inthe description of the light-emitting element 1 in Example 4 is to bereferred to. Chemical formulae of materials used in this example areshown below.

<<Fabrication of Light-Emitting Element 3>>

First, indium tin oxide containing silicon oxide (ITSO) was depositedover the glass substrate 1100 by a sputtering method, so that the firstelectrode 1101 which functions as an anode was formed. The thickness was110 nm and the electrode area was 2 mm×2 mm.

Then, as pretreatment for forming the light-emitting element over thesubstrate 1100, UV ozone treatment was performed for 370 seconds afterwashing of a surface of the substrate with water and baking that wasperformed at 200° C. for 1 hour.

After that, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to approximately 10⁻⁴ Pa,and was subjected to vacuum baking at 170° C. for 30 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate 1100 was cooled down for about 30 minutes.

Next, the substrate 1100 was fixed to a holder provided in the vacuumevaporation apparatus so that a surface of the substrate 1100 over whichthe first electrode 1101 was formed faced downward. In this example, acase will be described in which the hole-injection layer 1111, thehole-transport layer 1112, the light-emitting layer 1113, theelectron-transport layer 1114, and the electron-injection layer 1115which are included in the EL layer 1102 are sequentially formed by avacuum evaporation method.

After reducing the pressure of the vacuum evaporation apparatus to 10⁻⁴Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) andmolybdenum(VI) oxide were co-evaporated with a mass ratio of DBT3P-II(abbreviation) to molybdenum oxide being 4:2, whereby the hole-injectionlayer 1111 was formed over the first electrode 1101. The thickness ofthe hole-injection layer 1111 was 40 nm. Note that the co-evaporation isan evaporation method in which some different substances are evaporatedfrom some different evaporation sources at the same time.

Then, 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:BPAFLP) was deposited by evaporation to a thickness of 20 nm, so thatthe hole-transport layer 1112 was formed.

Next, the light-emitting layer 1113 was formed over the hole-transportlayer 1112 in the following manner. Co-evaporated were2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II), 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(abbreviation: NPB), andbis{2-[6-(3,5-dimethylphenyl)-4-pyrimidinyl-κN3]-4,6-dimethylphenyl-κC}(2,2′,6,6′-tetramethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppm)₂(dpm)]) with a mass ratio of 2mDBTPDBq-II(abbreviation) to NPB (abbreviation) and [Ir(dmdppm)₂(dpm)](abbreviation) being 0.8:0.2:0.025. The thickness of the light-emittinglayer 1113 was 40 nm.

Then, over the light-emitting layer 1113, 2mDBTPDBq-II (abbreviation)was deposited by evaporation to a thickness of 10 nm and thenbathophenanthroline (abbreviation: BPhen) was deposited by evaporationto a thickness of 20 nm, whereby the electron-transport layer 1114having a stacked structure was formed. Furthermore, lithium fluoride wasdeposited by evaporation to a thickness of 1 nm over theelectron-transport layer 1114, whereby the electron-injection layer 1115was formed.

Finally, aluminum was deposited by evaporation to a thickness of 200 nmover the electron-injection layer 1115 to form the second electrode 1103serving as a cathode; thus, the light-emitting element 3 was obtained.Note that in all the above evaporation steps, evaporation was performedby a resistance-heating method.

An element structure of the light-emitting element 3 obtained asdescribed above is shown in Table 5.

TABLE 5 Hole- Light- Electron- First Hole-injection transport emittingElectron- injection Second Electrode Layer Layer Layer transport LayerLayer Electrode Light- ITSO DBT3P-II:MoO_(x) BPAFLP * ** BPhen LiF Alemitting (110 nm) (4:2 40 nm) (20 nm) (20 nm) (1 nm) (200 nm) Element3 * 2mDBTPDBq-II:NPB:[Ir(dmdppm)₂(dpm)] (0.8:0.2:0.05 40 nm) **2mDBTPDBq-II (10 nm)

Further, the fabricated light-emitting element 3 was sealed in a glovebox containing a nitrogen atmosphere so as not to be exposed to the air(specifically, a sealant was applied onto an outer edge of the elementand heat treatment was performed at 80° C. for 1 hour at the time ofsealing).

<<Operation Characteristics of Light-Emitting Element 3>>

Operation characteristics of the fabricated light-emitting element 3were measured. Note that the measurement was carried out at roomtemperature (under an atmosphere in which the temperature was kept at25° C.).

FIG. 30 shows current density-luminance characteristics of thelight-emitting element 3. In FIG. 30, the vertical axis representsluminance (cd/m²) and the horizontal axis represents current density(mA/cm²). FIG. 31 shows voltage-luminance characteristics of thelight-emitting element 3. In FIG. 31, the vertical axis representsluminance (cd/m²) and the horizontal axis represents voltage (V).Further, FIG. 32 shows luminance-current efficiency characteristics ofthe light-emitting element 3. In FIG. 32, the vertical axis representscurrent efficiency (cd/A) and the horizontal axis represents luminance(cd/m²). FIG. 33 shows voltage-current characteristics of thelight-emitting element 3. In FIG. 33, the vertical axis representscurrent (mA) and the horizontal axis represents voltage (V).

FIG. 32 reveals high efficiency of the light-emitting element 3 in whichpart of the light-emitting layer uses [Ir(dmdppm)₂(dpm)] (abbreviation),the organometallic complex that is one embodiment of the presentinvention. Table 6 shows initial values of main characteristics of thelight-emitting element 3 at a luminance of about 1000 cd/m².

TABLE 6 Current Current Power Quantum Voltage Current DensityChromaticity Luminance Efficiency Efficiency Efficiency (V) (mA)(mA/cm²) (x, y) (cd/m²) (cd/A) (lm/W) (%) Light- 3 0.091 2.3 (0.62,0.38) 1200 52 55 30.3 emitting Element 3

The above results show that the light-emitting element 3 fabricated inthis example is a high-luminance light-emitting element having highcurrent efficiency. Moreover, as for color purity, it can be found thatthe light-emitting element exhibits reddish orange light emission withexcellent color purity.

FIG. 34 shows an emission spectrum when a current at a current densityof 2.5 mA/cm² was supplied to the light-emitting element 3. As shown inFIG. 34, the emission spectrum of the light-emitting element 3 has apeak at around 610 nm and it is indicated that the peak is derived fromemission of the organometallic complex [Ir(dmdppm)₂(dpm)](abbreviation). Note that FIG. 34 also shows an emission spectrum of acomparative light-emitting element 3 as a comparative example. Thecomparative light-emitting element 3 was fabricated using anorganometallic complex [Ir(dppm)₂(acac)] (abbreviation) instead of theorganometallic complex [Ir(dmdppm)₂(dpm)] (abbreviation) which was usedin the light-emitting element 3. Thus, it was observed that half widthof the emission spectrum of the light-emitting element 3 is smaller thanthat in the emission spectrum of the comparative light-emitting element3. This can be presumed to be an effect brought about by the structureof the organometallic complex [Ir(dmdppm)₂(dpm)] (abbreviation), inwhich methyl groups are bonded to the 2-position and the 4-position ofthe phenyl group bonded to iridium. Therefore, it can be said that thelight-emitting element 3 has high emission efficiency and achieves highcolor purity.

The light-emitting element 3 was subjected to reliability tests. Resultsof the reliability tests are shown in FIG. 35 and FIG. 36. In FIG. 35,the vertical axis represents normalized luminance (%) with an initialluminance of 100% and the horizontal axis represents driving time (h) ofthe element. Note that in one of the reliability tests, thelight-emitting element 3 was driven under the conditions where theinitial luminance was set to 5000 cd/m² and the current density wasconstant. The light-emitting element 3 kept about 85% of the initialluminance after 100 hours elapsed. Further, in FIG. 36, the verticalaxis represents normalized luminance (%) with an initial luminance of100% and the horizontal axis represents driving time (h) of the element.Note that in the other of the reliability tests, the light-emittingelement 3 was driven with a current value of 0.3 mA. The light-emittingelement 3 kept about 90% of the initial luminance after 100 hourselapsed.

Thus, both of the reliability tests which were conducted under differentconditions showed that the light-emitting element 3 is highly reliable.In addition, it was confirmed that with the use of the organometalliccomplex that is one embodiment of the present invention, alight-emitting element with a long lifetime can be obtained.

Example 7

In this example, phosphorescent spectra which were obtained bycalculation will be described. Note that chemical formulae oforganometallic complexes used in this example are shown below.

Calculation Example

The most stable structures of [Ir(ppr)₂(acac)] (abbreviation) in asinglet ground state (S₀) and the lowest excited triplet state (T₁) andthe most stable structures of [Ir(dmppr)₂(acac)] (abbreviation), whichis an analogue model of the organometallic complex that is oneembodiment of the present invention, in a singlet ground state (S₀) andthe lowest excited triplet state (T₁) were calculated using the densityfunctional theory (DFT). In addition, a vibration analysis was conductedon each of the most stable structures, and probability of transitionbetween vibrational states in the S₀ and T₁ states was obtained, so thatthe phosphorescent spectra were calculated. In the DFT, the total energyis represented as the sum of potential energy, electrostatic energybetween electrons, electronic kinetic energy, and exchange-correlationenergy including all the complicated interactions between electrons.Also in the DFT, an exchange-correlation interaction is approximated bya functional (function of another function) of one electron potentialrepresented in terms of electron density to enable high-speedcalculations. Here, B3PW91, which is a hybrid functional, was used tospecify the weight of each parameter related to exchange-correlationenergy.

In addition, as basis functions, 6-311G (a basis function of atriple-split valence basis set using three contraction functions for avalence orbital) was applied to each of H, C, N, and O atoms, andLanL2DZ was applied to an Ir atom. By the above basis function, forexample, orbits of 1s to 3s are considered in the case of hydrogen atomswhile orbits of 1s to 4s and 2p to 4p are considered in the case ofcarbon atoms. Further, to improve calculation accuracy, the p functionand the d function as polarization basis sets were added to hydrogenatoms and atoms other than hydrogen atoms, respectively. Note thatGaussian 09 was used as a quantum chemistry computational program. Ahigh performance computer (Altix 4700, manufactured by SGI Japan, Ltd.)was used for the calculations.

Note that the phosphorescent spectra, which were obtained by the abovecalculation method, of [Ir(ppr)₂(acac)] (abbreviation) and[Ir(dmppr)₂(acac)] (abbreviation) which is an analogue model of theorganometallic complex that is one embodiment of the present inventionare shown in FIG. 38. The calculations were conducted with a half widthof 135 cm⁻¹, taking the Franck-Condon factor into account.

As shown in FIG. 38, the intensity of the secondary peak at around 640nm in the phosphorescent spectrum of [Ir(ppr)₂(acac)] (abbreviation) ishigh, whereas the intensity of the secondary peak at around 690 nm inthe phosphorescent spectrum of [Ir(dmppr)₂(acac)] (abbreviation) is low.The secondary peaks are ascribed to stretching vibration of a C—C bondor a C—N bond in the ligand. In [Ir(dmppr)₂(acac)] (abbreviation),probability of transition between vibrational states of such stretchingvibration is low. It can be seen that, accordingly, the spectrum of[Ir(dmppr)₂(acac)] (abbreviation), the analogue model of theorganometallic complex that is one embodiment of the present invention,is narrower than that of [Ir(ppr)₂(acac)] (abbreviation).

A dihedral angle formed by carbon atoms of the benzene ring was comparedbetween [Ir(ppr)₂(acac)] (abbreviation) and [Ir(dmppr)₂(acac)](abbreviation), the analogue model of the organometallic complexaccording to one embodiment of the present invention, which wereobtained by the above calculation method. The results of the comparisonare shown in Table 7. The positions of the dihedral angles each of whichwas formed by carbon atoms of the benzene ring and which were comparedto each other are shown in FIG. 39.

TABLE 7 [Ir(ppr)₂(acac)] [Ir(dmppr)₂(acac)] S₀ 1.2° 3.8° T₁ −1.7° 6.1°

The values of the dihedral angles in [Ir(ppr)₂(acac)] (abbreviation) inthe S₀ and T₁ states are small as shown in Table 7, which indicates thatthe benzene ring thereof is highly planar, and that probability oftransition between vibrational states of stretching vibration of the C—Cbond or the C—N bond in the ligand is high. In contrast, the values ofthe dihedral angles in [Ir(dmppr)₂(acac)] (abbreviation) in the S₀ andT₁ states are large, which indicates that the benzene ring thereof isless planar, and that probability of transition between vibrationalstates of stretching vibration of the C—C bond or the C—N bond in theligand is low. This can be attributed to the two methyl groups bonded tothe phenyl group. In other words, it was found that when two alkylgroups are bonded to the 2-position and the 4-position of a phenyl groupbonded to iridium, half width of a phosphorescent spectrum is small andcolor purity of emitted light is high.

Example 8 Synthesis Example 4

In Synthesis Example 4, a synthesis method ofbis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-KN]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III) (abbreviation:[Ir(dmdppr-P)₂(acac)]), the organometallic complex which is oneembodiment of the present invention represented by Structural Formula(121) in Embodiment 1, is described. The structure of[Ir(dmdppr-P)₂(acac)] (abbreviation) is shown below.

Step 1: Synthesis ofDi-μ-chloro-tetrakis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}diiridium(III)(abbreviation: [Ir(dmdppr-P)₂Cl]₂)

First, into a round-bottom flask equipped with a reflux pipe were put 30mL of 2-ethoxyethanol, 10 mL of water, 3.18 g of Hdmdppr-P(abbreviation), and 1.27 g of iridium chloride hydrate (IrCl₃.H₂O)(produced by Sigma-Aldrich Corporation), and the air in the flask wasreplaced with argon. After that, irradiation with microwaves (2.45 GHz,100 W) was performed for 1 hour to cause a reaction. The solvent wasdistilled off, and then the obtained residue was suction-filtered andwashed with ethanol to give [Ir(dmdppr-P)₂Cl]₂ (abbreviation) that is adinuclear complex as a reddish brown powder in a yield of 67%. Asynthesis scheme of Step 1 is shown in (d-1).

Step 2: Synthesis ofBis{4,6-dimethyl-2[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-P)₂(acac)])

Further, into a round-bottom flask equipped with a reflux pipe were put40 mL of 2-ethoxyethanol, 2.8 g of [Ir(dmdppr-P)₂Cl]₂ (abbreviation)that is the dinuclear complex obtained in Step 1, 0.46 g ofacetylacetone (abbreviation: Hacac), and 1.6 g of sodium carbonate, andthe air in the flask was replaced with argon. After that, heating wasperformed by irradiation with microwaves (2.45 GHz, 120 W) for 1 hour.The solvent was distilled off, and the obtained residue wassuction-filtered with ethanol and washed with water and ethanol. Theobtained solid was purified by flash column chromatography using ethylacetate and hexane as a developing solvent in a ratio of 1:10, andrecrystallization was carried out with a mixed solvent ofdichloromethane and ethanol, so that [Ir(dmdppr-P)₂(acac)](abbreviation), the organometallic complex that is one embodiment of thepresent invention, was obtained as a dark red powder in a yield of 24%.A synthesis scheme of Step 2 is shown in (d-2).

An analysis result by nuclear magnetic resonance (¹H-NMR) spectroscopyof the dark red powder obtained in Step 2 is described below. FIG. 40shows the ¹H-NMR chart. These results revealed that[Ir(dmdppr-P)₂(acac)] (abbreviation), the organometallic complex whichis one embodiment of the present invention represented by StructuralFormula (121), was obtained in Synthesis Example 4.

¹H-NMR. δ(CDCl₃): 1.41 (s, 6H), 1.81 (s, 6H), 1.95 (s, 6H), 2.42 (s,12H), 5.06 (s, 1H), 6.46 (s, 2H), 6.81 (s, 2H), 7.19 (s, 2H), 7.41-7.49(m, 10H), 8.05 (d, 4H), 8.83 (s, 2H).

Next, an ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as an “absorption spectrum”) of a dichloromethane solutionof [Ir(dmdppr-P)₂(acac)] (abbreviation) and an emission spectrum thereofwere measured. The measurement of the absorption spectrum was conductedat room temperature, for which an ultraviolet-visible lightspectrophotometer (V550 type manufactured by Japan SpectroscopyCorporation) was used and the dichloromethane solution (0.085 mmol/L)was put in a quartz cell. In addition, the measurement of the emissionspectrum was conducted at room temperature, for which a fluorescencespectrophotometer (FS920 manufactured by Hamamatsu Photonics K. K.) wasused and the degassed dichloromethane solution (0.085 mmol/L) was put ina quartz cell. Measurement results of the obtained absorption andemission spectra are shown in FIG. 41, in which the horizontal axisrepresents wavelength and the vertical axes represent absorptionintensity and emission intensity. In FIG. 41 where there are two solidlines, the thin line represents the absorption spectrum and the thickline represents the emission spectrum. Note that the absorption spectrumin FIG. 41 is the results obtained in such a way that the absorptionspectrum measured by putting only dichloromethane in a quartz cell wassubtracted from the absorption spectrum measured by putting thedichloromethane solution (0.085 mmol/L) in a quartz cell.

As shown in FIG. 41, [Ir(dmdppr-P)₂(acac)] (abbreviation), theorganometallic complex that is one embodiment of the present invention,has an emission peak at around 633 nm, and red light emission wasobserved from the dichloromethane solution.

Further, weight loss percentage of [Ir(dmdppr-P)₂(acac)] (abbreviation)was measured by a high vacuum differential type differential thermalbalance (TG/DTA 2410SA, manufactured by Bruker AXS K.K.). Thetemperature was increased at a rate of 10° C./min under a degree ofvacuum of 8×10⁻⁴ Pa. As a result, the weight loss percentage of[Ir(dmdppr-P)₂(acac)] (abbreviation), the organometallic complex that isone embodiment of the present invention, was found to be 100% as shownin FIG. 42, which indicated a favorable sublimation property of theorganometallic complex.

Example 9 Synthesis Example 5

In Synthesis Example 5, a synthesis method ofbis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-dmp)₂(acac)]), the organometallic complexwhich is one embodiment of the present invention represented byStructural Formula (122) in Embodiment 1, is described. The structure of[Ir(dmdppr-dmp)₂(acac)] (abbreviation) is shown below.

Step 1: Synthesis of 2,3-Bis(3,5-dimethylphenyl)pyrazine (abbreviation:Hdmdppr)

First, 5.00 g of 2,3-dichloropyrazine, 10.23 g of3,5-dimethylphenylboronic acid, 7.19 g of sodium carbonate, 0.29 g ofbis(triphenylphosphine)palladium(II) dichloride (Pd(PPh₃)₂Cl₂), 20 mL ofwater, and 20 mL of acetonitrile were put into a recovery flask equippedwith a reflux pipe, and the air in the flask was replaced with argon.This reaction container was subjected to irradiation with microwaves(2.45 GHz, 100 W) for 60 minutes to be heated. Here, into the flask werefurther put 2.55 g of 3,5-dimethylphenylboronic acid, 1.80 g of sodiumcarbonate, 0.070 g of Pd(PPh₃)₂Cl₂, 5 mL of water, and 5 mL ofacetonitrile, and irradiation with microwaves (2.45 GHz, 100 W) wasperformed again for 60 minutes so that heating was performed. Then,water was added to this solution and the organic layer was extractedwith dichloromethane. The obtained organic layer was washed with asaturated aqueous solution of sodium hydrogen carbonate, water, andsaturated brine, and was dried with magnesium sulfate. After the drying,the solution was filtered. The solvent of this solution was distilledoff, and the obtained residue was purified by flash columnchromatography using hexane and ethyl acetate as a developing solvent ina ratio of 5:1. The solvent was distilled off, and the obtained solidwas purified by flash column chromatography using dichloromethane andethyl acetate as a developing solvent in a ratio of 10:1, so thatHdmdppr (abbreviation), which was the pyrazine derivative to beproduced, was obtained as a white powder in a yield of 44%. Note thatthe irradiation with microwaves was performed using a microwavesynthesis system (Discover, manufactured by CEM Corporation). Asynthesis scheme of Step 1 is shown in (e-1).

Step 2: Synthesis of5-(2,6-Dimethylphenyl)-2,3-bis(3,5-dimethylphenyl)pyrazine(abbreviation: Hdmdppr-dmp)

Then, 2.81 g of 2-bromo-m-xylene and 30 mL of dry THF were put into a200 mL three-neck flask and the air in the flask was replaced withnitrogen. After the flask was cooled down to −78° C., 9.4 mL of n-butyllithium (1.6M solution of n-butyl lithium in hexane) was added dropwise,and the mixture was stirred at −78° C. for 1 hour. Here, 4.01 g ofHdmdppr (abbreviation) obtained in Step 1 and 40 mL of dry THF wereadded, and the mixture was stirred at room temperature for 16.5 hours.The reacted solution was poured into water and the solution wassubjected to extraction with chloroform. The obtained organic layer waswashed with water and saturated brine, and dried with magnesium sulfate.Manganese oxide was added to the obtained mixture and the mixture wasstirred for 30 minutes. Then, the solution was filtered and the solventwas distilled off. The obtained residue was purified by silica gelcolumn chromatography using dichloromethane and hexane as a developingsolvent in a ratio of 1:1, so that Hdmdppr-dmp (abbreviation), which wasthe pyrazine derivative to be produced, was obtained as a yellow whitepowder in a yield of 10%. A synthesis scheme of Step 2 is shown in(e-2).

Step 3: Synthesis ofDi-μ-chloro-tetrakis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}diiridium(III)(abbreviation: [Ir(dmdppr-dmp)₂Cl]₂)

Next, into a recovery flask equipped with a reflux pipe were put 15 mLof 2-ethoxyethanol, 5 mL of water, 1.12 g of Hdmdppr-dmp (abbreviation)obtained in Step 2, and 0.39 g of iridium chloride hydrate (IrCl₃.H₂O)(produced by Sigma-Aldrich Corporation), and the air in the flask wasreplaced with argon. After that, irradiation with microwaves (2.45 GHz,100 W) was performed for 1 hour to cause a reaction. The solvent wasdistilled off, and then the obtained residue was suction-filtered andwashed with hexane to give [Ir(dmdppr-dmp)₂Cl]₂ (abbreviation) that is adinuclear complex as a reddish brown powder in a yield of 98%. Asynthesis scheme of Step 3 is shown in (e-3).

Step 4: Synthesis ofBis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-dmp)₂(acac)])

Further, into a recovery flask equipped with a reflux pipe were put 30mL of 2-ethoxyethanol, 1.28 g of [Ir(dmdppr-dmp)₂Cl]₂ (abbreviation)that is the dinuclear complex obtained in Step 3, 0.19 g ofacetylacetone (abbreviation: Hacac), and 0.68 g of sodium carbonate, andthe air in the flask was replaced with argon. After that, heating wasperformed by irradiation with microwaves (2.45 GHz, 120 W) for 60minutes. The solvent was distilled off, and the obtained residue wassuction-filtered with ethanol. The obtained solid was washed with waterand ethanol. The obtained solid was dissolved in dichloromethane andfiltered through a filter aid in which Celite, alumina, and Celite werestacked in that order. Then, recrystallization was carried out with amixed solvent of dichloromethane and ethanol; thus,[Ir(dmdppr-dmp)₂(acac)] (abbreviation), the organometallic complex thatis one embodiment of the present invention, was obtained as a red powderin a yield of 51%. A synthesis scheme of Step 4 is shown in (e-4).

An analysis result by nuclear magnetic resonance (¹H-NMR) spectroscopyof the red powder obtained in Step 4 is described below. FIG. 43 showsthe ¹H-NMR chart. These results revealed that [Ir(dmdppr-dmp)₂(acac)](abbreviation), the organometallic complex which is one embodiment ofthe present invention represented by Structural Formula (122), wasobtained in Synthesis Example 5.

¹H-NMR. δ(CDCl₃): 1.48 (s, 6H), 1.75 (s, 6H), 1.94 (s, 6H), 2.12 (s,12H), 2.35 (s, 12H), 5.17 (s, 1H), 6.47 (s, 2H), 6.81 (s, 2H), 7.08 (d,4H), 7.12 (s, 2H), 7.18 (t, 2H), 7.40 (s, 4H), 8.36 (s, 2H).

Next, an ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as an “absorption spectrum”) of a dichloromethane solutionof [Ir(dmdppr-dmp)₂(acac)] (abbreviation) and an emission spectrumthereof were measured. The measurement of the absorption spectrum wasconducted at room temperature, for which an ultraviolet-visible lightspectrophotometer (V550 type manufactured by Japan SpectroscopyCorporation) was used and the dichloromethane solution (0.062 mmol/L)was put in a quartz cell. In addition, the measurement of the emissionspectrum was conducted at room temperature, for which a fluorescencespectrophotometer (FS920 manufactured by Hamamatsu Photonics K. K.) wasused and the degassed dichloromethane solution (0.062 mmol/L) was put ina quartz cell. Measurement results of the obtained absorption andemission spectra are shown in FIG. 44, in which the horizontal axisrepresents wavelength and the vertical axes represent absorptionintensity and emission intensity. In FIG. 44 where there are two solidlines, the thin line represents the absorption spectrum and the thickline represents the emission spectrum. Note that the absorption spectrumin FIG. 44 is the results obtained in such a way that the absorptionspectrum measured by putting only dichloromethane in a quartz cell wassubtracted from the absorption spectrum measured by putting thedichloromethane solution (0.062 mmol/L) in a quartz cell.

As shown in FIG. 44, [Ir(dmdppr-dmp)₂(acac)] (abbreviation), theorganometallic complex that is one embodiment of the present invention,has an emission peak at around 610 nm, and reddish orange light emissionwas observed from the dichloromethane solution.

Further, weight loss percentage of [Ir(dmdppr-dmp)₂(acac)](abbreviation) was measured by a high vacuum differential typedifferential thermal balance (TG/DTA 2410SA, manufactured by Bruker AXSK.K.). The temperature was increased at a rate of 10° C./min under adegree of vacuum of 8×10⁻⁴ Pa. As a result, the weight loss percentageof [Ir(dmdppr-dmp)₂(acac)] (abbreviation), the organometallic complexthat is one embodiment of the present invention, was found to be 100% asshown in FIG. 45, which indicated a favorable sublimation property ofthe organometallic complex.

Next, [Ir(dmdppr-dmp)₂(acac)] (abbreviation) obtained in this examplewas analyzed by liquid chromatography mass spectrometry (LC/MS).

In the analysis by LC/MS, liquid chromatography (LC) separation wascarried out with ACQUITY UPLC (manufactured by Waters Corporation) andmass spectrometry (MS) analysis was carried out with Xevo G2 Tof MS(manufactured by Waters Corporation). ACQUITY UPLC BEH C8 (2.1×100 mm,1.7 μm) was used as a column for the LC separation, and the columntemperature was 40° C. Acetonitrile was used for Mobile Phase A and a0.1% formic acid aqueous solution was used for Mobile Phase B. Further,a sample was prepared in such a manner that [Ir(dmdppr-dmp)₂(acac)](abbreviation) was dissolved in chloroform at a given concentration andthe mixture was diluted with acetonitrile. The injection amount was 5.0L.

In the LC separation, a gradient method in which the composition ofmobile phases is changed was employed. The ratio of Mobile Phase A toMobile Phase B was 85:15 for 0 to 1 minute after the start of themeasurement, and then the composition was changed so that the ratio ofMobile Phase A to Mobile Phase B in the 10th minute was 95:5. Thecomposition was changed linearly.

In the MS analysis, ionization was carried out by an electrosprayionization (ESI) method. Capillary voltage and sample cone voltage wereset to 3.0 kV and 30 V, respectively. Detection was carried out in apositive mode. The mass range for the measurement was m/z=100 to 1200.

A component with m/z of 1075.45 which underwent the separation and theionization under the above-described conditions was collided with anargon gas in a collision cell to dissociate into product ions. Energy(collision energy) for the collision with argon was 70 eV. The detectionresult of the dissociated product ions by time-of-flight (TOF) MS areshown in FIG. 46.

The results in FIG. 46 show that product ions of [Ir(dmdppr-dmp)₂(acac)](abbreviation), the organometallic complex that is one embodiment of thepresent invention represented by Structural Formula (122), were detectedmainly around m/z 973.38, m/z 957.35, m/z 679.18, m/z 577.13, and m/z477.10. Note that the results in FIG. 46 show characteristics derivedfrom [Ir(dmdppr-dmp)₂(acac)] (abbreviation) and therefore can beregarded as important data for identifying [Ir(dmdppr-dmp)₂(acac)](abbreviation) contained in the mixture.

It is presumed that the product ion around m/z 973.38 is a cation in astate where acetylacetone and a proton were eliminated from the compoundrepresented by Structural Formula (122), and this is characteristic ofthe organometallic complex that is one embodiment of the presentinvention. It is presumed that the product ion around m/z 957.35resulted from elimination of a methyl group from the product ion aroundm/z 973.38, which suggests that [Ir(dmdppr-dmp)₂(acac)] (abbreviation),the organometallic complex that is one embodiment of the presentinvention, includes a methyl group.

Example 10 Synthesis Example 6

In Synthesis Example 6, a synthesis method ofbis{4,6-dimethyl-2-[3,5-bis(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmtppr)₂(dibm)]), the organometallic complex which isone embodiment of the present invention represented by StructuralFormula (123) in Embodiment 1, is described. The structure of[Ir(dmtppr)₂(dibm)] (abbreviation) is shown below.

Step 1: Synthesis of 2,3-Bis(3,5-dimethylphenyl)pyrazine (abbreviation:Hdmdppr)

First, 5.00 g of 2,3-dichloropyrazine, 10.23 g of3,5-dimethylphenylboronic acid, 7.19 g of sodium carbonate, 0.29 g ofbis(triphenylphosphine)palladium(II) dichloride (Pd(PPh₃)₂Cl₂), 20 mL ofwater, and 20 mL of acetonitrile were put into a recovery flask equippedwith a reflux pipe, and the air in the flask was replaced with argon.This reaction container was subjected to irradiation with microwaves(2.45 GHz, 100 W) for 60 minutes to be heated. Here, into the flask werefurther put 2.55 g of 3,5-dimethylphenylboronic acid, 1.80 g of sodiumcarbonate, 0.070 g of Pd(PPh₃)₂Cl₂, 5 mL of water, and 5 mL ofacetonitrile, and irradiation with microwaves (2.45 GHz, 100 W) wasperformed again for 60 minutes so that heating was performed. Then,water was added to this solution and the organic layer was extractedwith dichloromethane. The obtained organic layer was washed with asaturated aqueous solution of sodium hydrogen carbonate, water, andsaturated brine, and was dried with magnesium sulfate. After the drying,the solution was filtered. The solvent of this solution was distilledoff, and the obtained residue was purified by flash columnchromatography using hexane and ethyl acetate as a developing solvent ina ratio of 5:1. The solvent was distilled off, and the obtained solidwas purified by flash column chromatography using dichloromethane andethyl acetate as a developing solvent in a ratio of 10:1, so thatHdmdppr (abbreviation), which was the pyrazine derivative to beproduced, was obtained as a white powder in a yield of 44%. Note thatthe irradiation with microwaves was performed using a microwavesynthesis system (Discover, manufactured by CEM Corporation). Asynthesis scheme of Step 1 is shown in (f-1).

Step 2: Synthesis of 2,3,5-Tris(3,5-dimethylphenyl)pyrazine(abbreviation: Hdmtppr)

First, 2.81 g of 5-bromo-m-xylene and 30 mL of dry THF were put into a200 mL three-neck flask and the air in the flask was replaced withnitrogen. After the flask was cooled down to −78° C., 9.4 mL of n-butyllithium (1.6M solution of n-butyl lithium in hexane) was added dropwise,and the mixture was stirred at −78° C. for 1 hour. Here, 4.02 g ofHdmdppr (abbreviation) obtained in Step 1 and 40 mL of dry THF wereadded, and the mixture was stirred at room temperature for 18 hours. Thereacted solution was poured into water and the solution was subjected toextraction with chloroform. The obtained organic layer was washed withwater and saturated brine, and dried with magnesium sulfate. Manganeseoxide was added to the obtained mixture and the mixture was stirred for30 minutes. Then, the solution was filtered and the solvent wasdistilled off. The obtained residue was purified by silica gel columnchromatography using dichloromethane and hexane as a developing solventin a ratio of 1:1, so that Hdmtppr (abbreviation), which was thepyrazine derivative to be produced, was obtained as an orange oil in ayield of 37%. A synthesis scheme of Step 2 is shown in (f-2).

Step 3: Synthesis ofDi-μ-chloro-tetrakis{4,6-dimethyl-2-[3,5-bis(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}diiridium(III)(abbreviation: [Ir(dmtppr)₂Cl]₂)

Next, into a recovery flask equipped with a reflux pipe were put 30 mLof 2-ethoxyethanol, 10 mL of water, 1.95 g of Hdmtppr (abbreviation)obtained in Step 2, and 0.72 g of iridium chloride hydrate (IrCl₃.H₂O)(produced by Sigma-Aldrich Corporation), and the air in the flask wasreplaced with argon. After that, irradiation with microwaves (2.45 GHz,100 W) was performed for 1 hour to cause a reaction. The solvent wasdistilled off, and then the obtained residue was suction-filtered andwashed with ethanol to give [Ir(dmtppr)₂Cl]₂ (abbreviation) that is adinuclear complex as a reddish brown powder in a yield of 78%. Asynthesis scheme of Step 3 is shown in (f-3).

Step 4: Synthesis ofBis{4,6-dimethyl-2-[3,5-bis(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmtppr)₂(dibm)])

Further, into a recovery flask equipped with a reflux pipe were put 30mL of 2-ethoxyethanol, 0.89 g of [Ir(dmtppr)₂Cl]₂ (abbreviation) that isthe dinuclear complex obtained in Step 3, 0.20 g of diisobutyrylmethane(abbreviation: Hdibm), and 0.47 g of sodium carbonate, and the air inthe flask was replaced with argon. Then, irradiation with microwaves(2.45 GHz, 200 W) was performed for 60 minutes. Here, 0.20 g of Hdibmwas added, and irradiation with microwaves (2.45 GHz, 200 W) wasperformed again for 60 minutes. The solvent was distilled off and 0.20 gof Hdibm, 0.47 g of sodium carbonate, and 30 mL of 2-ethoxyethanol wereadded. The air in the flask was replaced with argon. After that, heatingwas performed by irradiation with microwaves (2.45 GHz, 200 W) for 2hours. The solvent was distilled off, and the obtained residue wassuction-filtered with ethanol. The obtained solid was washed with waterand ethanol. The obtained solid was dissolved in dichloromethane andfiltered through a filter aid in which Celite, alumina, and Celite werestacked in that order. Then, recrystallization was carried out with amixed solvent of dichloromethane and ethanol; thus, [Ir(dmtppr)₂(dibm)](abbreviation), the organometallic complex that is one embodiment of thepresent invention, was obtained as a dark red powder in a yield of 73%.A synthesis scheme of Step 4 is shown in (f-4).

An analysis result by nuclear magnetic resonance (¹H-NMR) spectroscopyof the dark red powder obtained in Step 4 is described below. FIG. 47shows the ¹H-NMR chart. These results revealed that [Ir(dmtppr)₂(dibm)](abbreviation), the organometallic complex which is one embodiment ofthe present invention represented by Structural Formula (123), wasobtained in Synthesis Example 6.

¹H-NMR. δ(CDCl₃): 0.78 (d, 6H), 0.99 (d, 6H), 1.41 (s, 6H), 1.96 (s,6H), 2.24-2.30 (m, 2H), 2.35 (s, 12H), 2.42 (s, 12H), 5.07 (s, 1H), 6.46(s, 2H), 6.78 (s, 2H), 7.04 (s, 2H), 7.18 (s, 2H), 7.47 (s, 2H), 7.49(s, 2H), 7.67 (s, 4H), 8.77 (s, 2H).

Next, an ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as an “absorption spectrum”) of a dichloromethane solutionof [Ir(dmtppr)₂(dibm)] (abbreviation) and an emission spectrum thereofwere measured. The measurement of the absorption spectrum was conductedat room temperature, for which an ultraviolet-visible lightspectrophotometer (V550 type manufactured by Japan SpectroscopyCorporation) was used and the dichloromethane solution (0.068 mmol/L)was put in a quartz cell. In addition, the measurement of the emissionspectrum was conducted at room temperature, for which a fluorescencespectrophotometer (FS920 manufactured by Hamamatsu Photonics K. K.) wasused and the degassed dichloromethane solution (0.31 μmol/L) was put ina quartz cell. Measurement results of the obtained absorption andemission spectra are shown in FIG. 48, in which the horizontal axisrepresents wavelength and the vertical axes represent absorptionintensity and emission intensity. In FIG. 48 where there are two solidlines, the thin line represents the absorption spectrum and the thickline represents the emission spectrum. Note that the absorption spectrumin FIG. 48 is the results obtained in such a way that the absorptionspectrum measured by putting only dichloromethane in a quartz cell wassubtracted from the absorption spectrum measured by putting thedichloromethane solution (0.068 mmol/L) in a quartz cell.

As shown in FIG. 48, [Ir(dmtppr)₂(dibm)] (abbreviation), theorganometallic complex that is one embodiment of the present invention,has an emission peak at around 629 nm, and reddish orange light emissionwas observed from the dichloromethane solution.

Next, [Ir(dmtppr)₂(dibm)] (abbreviation) obtained in this example wasanalyzed by liquid chromatography mass spectrometry (LC/MS).

In the analysis by LC/MS, liquid chromatography (LC) separation wascarried out with ACQUITY UPLC (manufactured by Waters Corporation) andmass spectrometry (MS) analysis was carried out with Xevo G2 Tof MS(manufactured by Waters Corporation). ACQUITY UPLC BEH C8 (2.1×100 mm,1.7 μm) was used as a column for the LC separation, and the columntemperature was 40° C. Acetonitrile was used for Mobile Phase A and a0.1% formic acid aqueous solution was used for Mobile Phase B. Further,a sample was prepared in such a manner that [Ir(dmtppr)₂(dibm)](abbreviation) was dissolved in chloroform at a given concentration andthe mixture was diluted with acetonitrile. The injection amount was 5.0pt.

In the LC separation, a gradient method in which the composition ofmobile phases is changed was employed. The ratio of Mobile Phase A toMobile Phase B was 90:10 for 0 to 1 minute after the start of themeasurement. Then, the composition was changed so that the ratio ofMobile Phase A to Mobile Phase B in the 2nd minute was 95:5, and theratio was kept the same until the 10th minute. The composition waschanged linearly.

In the MS analysis, ionization was carried out by an electrosprayionization (ESI) method. Capillary voltage and sample cone voltage wereset to 3.01075 kV and 30 V, respectively. Detection was carried out in apositive mode. The mass range for the measurement was m/z=100 to 1200.

A component with m/z of 1131.52 which underwent the separation and theionization under the above-described conditions was collided with anargon gas in a collision cell to dissociate into product ions. Energy(collision energy) for the collision with argon was 70 eV. The detectionresult of the dissociated product ions by time-of-flight (TOF) MS areshown in FIG. 49.

The results in FIG. 49 show that product ions of [Ir(dmtppr)₂(dibm)](abbreviation), the organometallic complex that is one embodiment of thepresent invention represented by Structural Formula (123), were detectedmainly around m/z 973.38 and m/z 583.17. Note that the results in FIG.49 show characteristics derived from [Ir(dmtppr)₂(dibm)] (abbreviation)and therefore can be regarded as important data for identifying[Ir(dmtppr)₂(dibm)] (abbreviation) contained in the mixture.

It is presumed that the product ion around m/z 973.38 is a cation in astate where acetylacetone and a proton were eliminated from the compoundrepresented by Structural Formula (123), and this is characteristic ofthe organometallic complex that is one embodiment of the presentinvention. Further, it is presumed that the product ion around m/z583.17 is a cation in a state where Hdmtppr-dmp (abbreviation) that isthe ligand and acetylacetone were eliminated from the compoundrepresented by Structural Formula (123), which is characteristic of theorganometallic complex that is one embodiment of the present invention.

Example 11 Synthesis Example 7

In Synthesis Example 7, a synthesis method ofbis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-dmp)₂(dibm)]), the organometallic complexwhich is one embodiment of the present invention represented byStructural Formula (124) in Embodiment 1, is described. The structure of[Ir(dmdppr-dmp)₂(dibm)] (abbreviation) is shown below.

Step 1: Synthesis of 2,3-Bis(3,5-dimethylphenyl)pyrazine (abbreviation:Hdmdppr)

First, 5.00 g of 2,3-dichloropyrazine, 10.23 g of3,5-dimethylphenylboronic acid, 7.19 g of sodium carbonate, 0.29 g ofbis(triphenylphosphine)palladium(II) dichloride (Pd(PPh₃)₂Cl₂), 20 mL ofwater, and 20 mL of acetonitrile were put into a recovery flask equippedwith a reflux pipe, and the air in the flask was replaced with argon.This reaction container was subjected to irradiation with microwaves(2.45 GHz, 100 W) for 60 minutes to be heated. Here, into the flask werefurther put 2.55 g of 3,5-dimethylphenylboronic acid, 1.80 g of sodiumcarbonate, 0.070 g of Pd(PPh₃)₂Cl₂, 5 mL of water, and 5 mL ofacetonitrile, and irradiation with microwaves (2.45 GHz, 100 W) wasperformed again for 60 minutes so that heating was performed. Then,water was added to this solution and the organic layer was extractedwith dichloromethane. The obtained organic layer was washed with asaturated aqueous solution of sodium hydrogen carbonate, water, andsaturated brine, and was dried with magnesium sulfate. After the drying,the solution was filtered. The solvent of this solution was distilledoff, and the obtained residue was purified by flash columnchromatography using hexane and ethyl acetate as a developing solvent ina ratio of 5:1. The solvent was distilled off, and the obtained solidwas purified by flash column chromatography using dichloromethane andethyl acetate as a developing solvent in a ratio of 10:1, so thatHdmdppr (abbreviation), which was the pyrazine derivative to beproduced, was obtained as a white powder in a yield of 44%. Note thatthe irradiation with microwaves was performed using a microwavesynthesis system (Discover, manufactured by CEM Corporation). Asynthesis scheme of Step 1 is shown in (g-1).

Step 2: Synthesis of5-(2,6-Dimethylphenyl)-2,3-bis(3,5-dimethylphenyl)pyrazine(abbreviation: Hdmdppr-dmp)

First, 2.81 g of 2-bromo-m-xylene and 30 mL of dry THF were put into a200 mL three-neck flask and the air in the flask was replaced withnitrogen. After the flask was cooled down to −78° C., 9.4 mL of n-butyllithium (1.6M solution of n-butyl lithium in hexane) was added dropwise,and the mixture was stirred at −78° C. for 1 hour. Here, 4.01 g ofHdmdppr (abbreviation) obtained in Step 1 and 40 mL of dry THF wereadded, and the mixture was stirred at room temperature for 16.5 hours.The reacted solution was poured into water and the solution wassubjected to extraction with chloroform. The obtained organic layer waswashed with water and saturated brine, and dried with magnesium sulfate.Manganese oxide was added to the obtained mixture and the mixture wasstirred for 30 minutes. Then, the solution was filtered and the solventwas distilled off. The obtained residue was purified by silica gelcolumn chromatography using dichloromethane and hexane as a developingsolvent in a ratio of 1:1, so that Hdmdppr-dmp (abbreviation), which wasthe pyrazine derivative to be produced, was obtained as a yellow whitepowder in a yield of 10%. A synthesis scheme of Step 2 is shown in(g-2).

Step 3: Synthesis of Di-μ-chloro-tetrakis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}diiridium(III)(abbreviation: [Ir(dmdppr-dmp)₂Cl]₂)

Next, into a recovery flask equipped with a reflux pipe were put 15 mLof 2-ethoxyethanol, 5 mL of water, 1.12 g of Hdmdppr-dmp (abbreviation)obtained in Step 2, and 0.39 g of iridium chloride hydrate (IrCl₃.H₂O)(produced by Sigma-Aldrich Corporation), and the air in the flask wasreplaced with argon. After that, irradiation with microwaves (2.45 GHz,100 W) was performed for 1 hour to cause a reaction. The solvent wasdistilled off, and then the obtained residue was suction-filtered andwashed with hexane to give [Ir(dmdppr-dmp)₂Cl]₂ (abbreviation) that is adinuclear complex as a reddish brown powder in a yield of 98%. Asynthesis scheme of Step 3 is shown in (g-3).

Step 4: Synthesis ofBis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-dmp)₂(dibm)])

Further, into a recovery flask equipped with a reflux pipe were put 30mL of 2-ethoxyethanol, 0.80 g of [Ir(dmdppr-dmp)₂Cl]₂ (abbreviation)that is the dinuclear complex obtained in Step 3, 0.19 g ofdiisobutyrylmethane (abbreviation: Hdibm), and 0.42 g of sodiumcarbonate, and the air in the flask was replaced with argon. After that,heating was performed by irradiation with microwaves (2.45 GHz, 120 W)for 60 minutes. The solvent was distilled off, and the obtained residuewas dissolved in dichloromethane and filtered through a filter aid inwhich Celite, alumina, and Celite were stacked in that order. Then,recrystallization was carried out with a mixed solvent ofdichloromethane and methanol; thus, [Ir(dmdppr-dmp)₂(dibm)](abbreviation), the organometallic complex that is one embodiment of thepresent invention, was obtained as a red powder in a yield of 48%. Asynthesis scheme of Step 4 is shown in (g-4).

An analysis result by nuclear magnetic resonance (¹H-NMR) spectroscopyof the red powder obtained in Step 4 is described below. FIG. 50 showsthe ¹H-NMR chart. These results revealed that [Ir(dmdppr-dmp)₂(dibm)](abbreviation), the organometallic complex which is one embodiment ofthe present invention represented by Structural Formula (124), wasobtained in Synthesis Example 7.

¹H-NMR. δ(CDCl₃): 0.80 (d, 6H), 0.81 (d, 6H), 1.47 (s, 6H), 1.95 (s,6H), 2.10 (s, 12H), 2.23-2.28 (m, 2H), 2.34 (s, 12H), 5.19 (s, 1H), 6.48(s, 2H), 6.81 (s, 2H), 7.06 (d, 4H), 7.11 (s, 2H), 7.16 (t, 2H), 7.40(s, 4H), 8.22 (s, 2H).

Next, an ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as an “absorption spectrum”) of a dichloromethane solutionof [Ir(dmdppr-dmp)₂(dibm)] (abbreviation) and an emission spectrumthereof were measured. The measurement of the absorption spectrum wasconducted at room temperature, for which an ultraviolet-visible lightspectrophotometer (V550 type manufactured by Japan SpectroscopyCorporation) was used and the dichloromethane solution (0.059 mmol/L)was put in a quartz cell. In addition, the measurement of the emissionspectrum was conducted at room temperature, for which a fluorescencespectrophotometer (FS920 manufactured by Hamamatsu Photonics K. K.) wasused and the degassed dichloromethane solution (0.059 mmol/L) was put ina quartz cell. Measurement results of the obtained absorption andemission spectra are shown in FIG. 51, in which the horizontal axisrepresents wavelength and the vertical axes represent absorptionintensity and emission intensity. In FIG. 51 where there are two solidlines, the thin line represents the absorption spectrum and the thickline represents the emission spectrum. Note that the absorption spectrumin FIG. 51 is the results obtained in such a way that the absorptionspectrum measured by putting only dichloromethane in a quartz cell wassubtracted from the absorption spectrum measured by putting thedichloromethane solution (0.059 mmol/L) in a quartz cell.

As shown in FIG. 51, [Ir(dmdppr-dmp)₂(dibm)] (abbreviation), theorganometallic complex that is one embodiment of the present invention,has an emission peak at around 616 nm, and reddish orange light emissionwas observed from the dichloromethane solution.

Further, weight loss percentage of [Ir(dmdppr-dmp)₂(dibm)](abbreviation) was measured by a high vacuum differential typedifferential thermal balance (TG/DTA 2410SA, manufactured by Bruker AXSK.K.). The temperature was increased at a rate of 10° C./min under adegree of vacuum of 1×10⁻³ Pa. As a result, the weight loss percentageof [Ir(dmdppr-dmp)₂(dibm)] (abbreviation), the organometallic complexthat is one embodiment of the present invention, was found to be 100% asshown in FIG. 52, which indicated a favorable sublimation property ofthe organometallic complex.

Next, [Ir(dmdppr-dmp)₂(dibm)] (abbreviation) obtained in this examplewas analyzed by liquid chromatography mass spectrometry (LC/MS).

In the analysis by LC/MS, liquid chromatography (LC) separation wascarried out with ACQUITY UPLC (manufactured by Waters Corporation) andmass spectrometry (MS) analysis was carried out with Xevo G2 Tof MS(manufactured by Waters Corporation). ACQUITY UPLC BEH C8 (2.1×100 mm,1.7 μm) was used as a column for the LC separation, and the columntemperature was 40° C. Acetonitrile was used for Mobile Phase A and a0.1% formic acid aqueous solution was used for Mobile Phase B. Further,a sample was prepared in such a manner that [Ir(dmdppr-dmp)₂(dibm)](abbreviation) was dissolved in chloroform at a given concentration andthe mixture was diluted with acetonitrile. The injection amount was 5.0μL.

In the LC separation, a gradient method in which the composition ofmobile phases is changed was employed. The ratio of Mobile Phase A toMobile Phase B was 90:10 for 0 to 1 minute after the start of themeasurement, and then the composition was changed so that the ratio ofMobile Phase A to Mobile Phase B in the 10th minute was 95:5. Thecomposition was changed linearly.

In the MS analysis, ionization was carried out by an electrosprayionization (ESI) method. Capillary voltage and sample cone voltage wereset to 3.0 kV and 30 V, respectively. Detection was carried out in apositive mode. The mass range for the measurement was m/z=100 to 1200.

A component with m/z of 1131.52 which underwent the separation and theionization under the above-described conditions was collided with anargon gas in a collision cell to dissociate into product ions. Energy(collision energy) for the collision with argon was 70 eV. The detectionresult of the dissociated product ions by time-of-flight (TOF) MS areshown in FIG. 53.

The results in FIG. 53 show that product ions of [Ir(dmdppr-dmp)₂(dibm)](abbreviation), the organometallic complex that is one embodiment of thepresent invention represented by Structural Formula (124), were detectedmainly around m/z 973.39, m/z 959.36, m/z 581.16, m/z 555.15, and m/z393.23. Note that the results in FIG. 53 show characteristics derivedfrom [Ir(dmdppr-dmp)₂(dibm)] (abbreviation) and therefore can beregarded as important data for identifying [Ir(dmdppr-dmp)₂(dibm)](abbreviation) contained in the mixture.

It is presumed that the product ion around m/z 973.38 is a cation in astate where acetylacetone and a proton were eliminated from the compoundrepresented by Structural Formula (124), and this is characteristic ofthe organometallic complex that is one embodiment of the presentinvention. It is presumed that the product ion around m/z 959.36resulted from elimination of a methyl group from the product ion aroundm/z 973.38, which suggests that [Ir(dmdppr-dmp)₂(dibm)] (abbreviation),the organometallic complex that is one embodiment of the presentinvention, includes a methyl group.

Example 12 Synthesis Example 8

In Synthesis Example 8, a synthesis method ofbis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,2′,6,6′-tetramethyl-3,5-heptanedionato-κ²O,O′)iridium(III) (abbreviation:[Ir(dmdppr-dmp)₂(dpm)]), the organometallic complex which is oneembodiment of the present invention represented by Structural Formula(125) in Embodiment 1, is described. The structure of[Ir(dmdppr-dmp)₂(dpm)] (abbreviation) is shown below.

Step 1: Synthesis of 2,3-Bis(3,5-dimethylphenyl)pyrazine (abbreviation:Hdmdppr)

First, 5.00 g of 2,3-dichloropyrazine, 10.23 g of3,5-dimethylphenylboronic acid, 7.19 g of sodium carbonate, 0.29 g ofbis(triphenylphosphine)palladium(II) dichloride (Pd(PPh₃)₂Cl₂), 20 mL ofwater, and 20 mL of acetonitrile were put into a recovery flask equippedwith a reflux pipe, and the air in the flask was replaced with argon.This reaction container was subjected to irradiation with microwaves(2.45 GHz, 100 W) for 60 minutes to be heated. Here, into the flask werefurther put 2.55 g of 3,5-dimethylphenylboronic acid, 1.80 g of sodiumcarbonate, 0.070 g of Pd(PPh₃)₂Cl₂, 5 mL of water, and 5 mL ofacetonitrile, and irradiation with microwaves (2.45 GHz, 100 W) wasperformed again for 60 minutes so that heating was performed. Then,water was added to this solution and the organic layer was extractedwith dichloromethane. The obtained organic layer was washed with asaturated aqueous solution of sodium hydrogen carbonate, water, andsaturated brine, and was dried with magnesium sulfate. After the drying,the solution was filtered. The solvent of this solution was distilledoff, and the obtained residue was purified by flash columnchromatography using hexane and ethyl acetate as a developing solvent ina ratio of 5:1. The solvent was distilled off, and the obtained solidwas purified by flash column chromatography using dichloromethane andethyl acetate as a developing solvent in a ratio of 10:1, so thatHdmdppr (abbreviation), which was the pyrazine derivative to beproduced, was obtained as a white powder in a yield of 44%. Note thatthe irradiation with microwaves was performed using a microwavesynthesis system (Discover, manufactured by CEM Corporation). Asynthesis scheme of Step 1 is shown in (h-1).

Step 2: Synthesis of 2,3-Bis(3,5-dimethylphenyl)pyrazin-1-oxide)

Next, 6.6 g of Hdmdppr (abbreviation) obtained in Step 1, 7.8 g of3-chloroperbenzoic acid, and 90 mL of dichloromethane were put into a300 mL three-neck flask, and the air in the flask was replaced withnitrogen. The mixture was stirred at room temperature for 24 hours, thereacted solution was then poured into water, and the solution wassubjected to extraction with dichloromethane. The obtained organic layerwas washed with a saturated aqueous solution of sodium hydrogencarbonate, and was dried with magnesium sulfate. After the drying, thesolution was filtered. The solvent of this solution was distilled off,whereby the pyrazine derivative to be produced was obtained as a yellowpowder in a yield of 100%. A synthesis scheme of Step 2 is shown in(h-2).

Step 3: Synthesis of 5-Chloro-2,3-bis(3,5-dimethylphenyl)pyrazine)

Then, 7.0 g of 2,3-bis(3,5-dimethylphenyl)pyrazin-1-oxide obtained inStep 2 was put into a 100 mL three-neck flask and the air in the flaskwas replaced with nitrogen. Here, 20 mL of phosphoryl chloride was addedand the mixture was stirred at 100° C. for 1 hour. The reacted solutionwas poured into water and the solution was subjected to extraction withchloroform. The obtained organic layer was washed with a saturatedaqueous solution of sodium hydrogen carbonate, water, and saturatedbrine, and dried with magnesium sulfate. After the drying, the solutionwas filtered. The solvent of this solution was distilled off, wherebythe pyrazine derivative to be produced was obtained as a gray powder ina yield of 90%. A synthesis scheme of Step 3 is shown in (h-3).

Step 4: Synthesis of5-(2,6-Dimethylphenyl)-2,3-bis(3,5-dimethylphenyl)pyrazine(abbreviation: Hdmdppr-dmp)

Then, 1.21 g of 5-chloro-2,3-bis(3,5-dimethylphenyl)pyrazine obtained inStep 3, 1.10 g of 2,6-dimethylphenylboronic acid, 0.78 g of sodiumcarbonate, 15 mg of Pd(PPh₃)₂Cl₂, 14 mL of water, and 14 mL ofacetonitrile were put into a recovery flask equipped with a reflux pipe,and the mixture was bubbled with argon for 15 minutes. This reactioncontainer was subjected to irradiation with microwaves (2.45 GHz, 100 W)for 3 hours. Here, into the flask were further put 0.55 g of2,6-dimethylphenylboronic acid, 0.39 g of sodium carbonate, and 7 mg ofPd(PPh₃)₂Cl₂, and the mixture was bubbled with argon for 15 minutes.This reaction container was subjected to irradiation with microwaves(2.45 GHz, 100 W) again for 3 hours to be heated. The mixture wassuction-filtered and the obtained solid was washed with ethanol. Theobtained solid was dissolved in dichloromethane and filtered through afilter aid in which Celite, alumina, and Celite were stacked in thatorder, so that Hdmdppr-dmp (abbreviation), which was the pyrazinederivative to be produced, was obtained as a white powder in a yield of89%. A synthesis scheme of Step 4 is shown in (h-4).

Step 5: Synthesis ofDi-μ-chloro-tetrakis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}diiridium(III)(abbreviation: [Ir(dmdppr-dmp)₂Cl]₂)

Next, into a recovery flask equipped with a reflux pipe were put 15 mLof 2-ethoxyethanol, 5 mL of water, 1.12 g of Hdmdppr-dmp (abbreviation)obtained in Step 4, and 0.39 g of iridium chloride hydrate (IrCl₃.H₂O)(produced by Sigma-Aldrich Corporation), and the air in the flask wasreplaced with argon. After that, irradiation with microwaves (2.45 GHz,100 W) was performed for 1 hour to cause a reaction. The solvent wasdistilled off, and then the obtained residue was suction-filtered andwashed with hexane to give [Ir(dmdppr-dmp)₂Cl]₂ (abbreviation) that is adinuclear complex as a reddish brown powder in a yield of 98%. Asynthesis scheme of Step 3 is shown in (h-5).

Step 6: Synthesis ofBis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,2′,6,6′-tetramethyl-3,5-heptanedionato-κ²O,O′)iridium(III) (abbreviation:[Ir(dmdppr-dmp)₂(dpm)])

Further, into a recovery flask equipped with a reflux pipe were put 30mL of 2-ethoxyethanol, 1.38 g of [Ir(dmdppr-dmp)₂Cl]₂ (abbreviation)that is the dinuclear complex obtained in Step 5, 0.39 g ofdipivaloylmethane (abbreviation: Hdpm), and 0.73 g of sodium carbonate,and the air in the flask was replaced with argon. After that, heatingwas performed by irradiation with microwaves (2.45 GHz, 120 W) for 60minutes. The solvent was distilled off, and the obtained residue wassuction-filtered with methanol. The obtained solid was washed with waterand methanol. The obtained solid was dissolved in dichloromethane andfiltered through a filter aid in which Celite, alumina, and Celite werestacked in that order. Then, recrystallization was carried out with amixed solvent of dichloromethane and methanol; thus,[Ir(dmdppr-dmp)₂(dpm)] (abbreviation), the organometallic complex thatis one embodiment of the present invention, was obtained as a dark redpowder in a yield of 59%. A synthesis scheme of Step 6 is shown in(h-6).

An analysis result by nuclear magnetic resonance (¹H-NMR) spectroscopyof the dark red powder obtained in Step 6 is described below. FIG. 54shows the ¹H-NMR chart. These results revealed that[Ir(dmdppr-dmp)₂(dpm)] (abbreviation), the organometallic complex whichis one embodiment of the present invention represented by StructuralFormula (125), was obtained in Synthesis Example 8.

¹H-NMR. δ(CDCl₃): 0.90 (s, 18H), 1.46 (s, 6H), 1.95 (s, 6H), 2.10 (s,12H), 2.34 (s, 12H), 5.57 (s, 1H), 6.47 (s, 2H), 6.81 (s, 2H), 7.06 (d,4H), 7.11 (s, 2H), 7.16 (t, 2H), 7.38 (s, 4H), 8.19 (s, 2H).

Next, an ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as an “absorption spectrum”) of a dichloromethane solutionof [Ir(dmdppr-dmp)₂(dpm)] (abbreviation) and an emission spectrumthereof were measured. The measurement of the absorption spectrum wasconducted at room temperature, for which an ultraviolet-visible lightspectrophotometer (V550 type manufactured by Japan SpectroscopyCorporation) was used and the dichloromethane solution (0.058 mmol/L)was put in a quartz cell. In addition, the measurement of the emissionspectrum was conducted at room temperature, for which a fluorescencespectrophotometer (FS920 manufactured by Hamamatsu Photonics K. K.) wasused and the degassed dichloromethane solution (0.058 mmol/L) was put ina quartz cell. Measurement results of the obtained absorption andemission spectra are shown in FIG. 55, in which the horizontal axisrepresents wavelength and the vertical axes represent absorptionintensity and emission intensity. In FIG. 55 where there are two solidlines, the thin line represents the absorption spectrum and the thickline represents the emission spectrum. Note that the absorption spectrumin FIG. 55 is the results obtained in such a way that the absorptionspectrum measured by putting only dichloromethane in a quartz cell wassubtracted from the absorption spectrum measured by putting thedichloromethane solution (0.058 mmol/L) in a quartz cell.

As shown in FIG. 55, [Ir(dmdppr-dmp)₂(dpm)] (abbreviation), theorganometallic complex that is one embodiment of the present invention,has an emission peak at around 618 nm, and reddish orange light emissionwas observed from the dichloromethane solution.

Further, weight loss percentage of [Ir(dmdppr-dmp)₂(dpm)] (abbreviation)was measured by a high vacuum differential type differential thermalbalance (TG/DTA 2410SA, manufactured by Bruker AXS K.K.). Thetemperature was increased at a rate of 10° C./min under a degree ofvacuum of 1×10⁻³ Pa. As a result, the weight loss percentage of[Ir(dmdppr-dmp)₂(dpm)] (abbreviation), the organometallic complex thatis one embodiment of the present invention, was found to be 97% as shownin FIG. 56, which indicated a favorable sublimation property of theorganometallic complex.

Example 13

In this example, the following light-emitting elements in each of whichan organometallic complex that is one embodiment of the presentinvention is used for a light-emitting layer will be described: alight-emitting element 4 in which [Ir(dmdppr-P)₂(acac)] (abbreviation)represented by Structural Formula (121) is used; a light-emittingelement 5 in which [Ir(dmdppr-dmp)₂(acac)] (abbreviation) represented byStructural Formula (122) is used; a light-emitting element 6 in which[Ir(dmtppr)₂(dibm)] (abbreviation) represented by Structural Formula(123) is used; and a light-emitting element 7 in which[Ir(dmdppr-dmp)₂(dibm)] (abbreviation) represented by Structural Formula(124) is used. Note that in the description of the light-emittingelements 4 to 7 in this example, FIG. 15 which is used in thedescription of the light-emitting element 1 in Example 4 is to bereferred to. Chemical formulae of materials used in this example areshown below.

<<Fabrication of Light-Emitting Elements 4 to 7>>

First, indium tin oxide containing silicon oxide (ITSO) was depositedover the glass substrate 1100 by a sputtering method, so that the firstelectrode 1101 which functions as an anode was formed. The thickness was110 nm and the electrode area was 2 mm×2 mm.

Then, as pretreatment for forming the light-emitting element over thesubstrate 1100, UV ozone treatment was performed for 370 seconds afterwashing of a surface of the substrate with water and baking that wasperformed at 200° C. for 1 hour.

After that, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to approximately 10⁻⁴ Pa,and was subjected to vacuum baking at 170° C. for 30 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate 1100 was cooled down for about 30 minutes.

Next, the substrate 1100 was fixed to a holder provided in the vacuumevaporation apparatus so that a surface of the substrate 1100 over whichthe first electrode 1101 was formed faced downward. In this example, acase will be described in which the hole-injection layer 1111, thehole-transport layer 1112, the light-emitting layer 1113, theelectron-transport layer 1114, and the electron-injection layer 1115which are included in the EL layer 1102 are sequentially formed by avacuum evaporation method.

After reducing the pressure of the vacuum evaporation apparatus to 10⁻⁴Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) andmolybdenum(VI) oxide were co-evaporated with a mass ratio of DBT3P-II(abbreviation) to molybdenum oxide being 4:2, whereby the hole-injectionlayer 1111 was formed over the first electrode 1101. The thickness ofthe hole-injection layer 1111 was 20 nm. Note that the co-evaporation isan evaporation method in which some different substances are evaporatedfrom some different evaporation sources at the same time.

Then, 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:BPAFLP) was deposited by evaporation to a thickness of 20 nm, so thatthe hole-transport layer 1112 was formed.

Next, the light-emitting layer 1113 was formed over the hole-transportlayer 1112 in the following manner. In the case of the light-emittingelement 4, co-evaporated were 2mDBTPDBq-II (abbreviation), NPB(abbreviation), and [Ir(dmdppr-P)₂(acac)] (abbreviation) with a massratio of 2mDBTPDBq-II (abbreviation) to NPB (abbreviation) and[Ir(dmdppr-P)₂(acac)] (abbreviation) being 0.8:0.2:0.05. The thicknessof the light-emitting layer 1113 was 40 nm. In the case of thelight-emitting element 5, co-evaporated were 2mDBTPDBq-II(abbreviation), NPB (abbreviation), and [Ir(dmdppr-dmp)₂(acac)](abbreviation) with a mass ratio of 2mDBTPDBq-II (abbreviation) to NPB(abbreviation) and [Ir(dmdppr-dmp)₂(acac)] (abbreviation) being0.8:0.2:0.05. The thickness of the light-emitting layer 1113 was 40 nm.In the case of the light-emitting element 6, co-evaporated were2mDBTPDBq-II (abbreviation), NPB (abbreviation), and [Ir(dmtppr)₂(dibm)](abbreviation) with a mass ratio of 2mDBTPDBq-II (abbreviation) to NPB(abbreviation) and [Ir(dmtppr)₂(dibm)] (abbreviation) being0.8:0.2:0.05. The thickness of the light-emitting layer 1113 was 40 nm.In the case of the light-emitting element 7, co-evaporated were2mDBTPDBq-II (abbreviation), NPB (abbreviation), and[Ir(dmdppr-dmp)₂(dibm)] (abbreviation) with a mass ratio of 2mDBTPDBq-II(abbreviation) to NPB (abbreviation) and [Ir(dmdppr-dmp)₂(dibm)](abbreviation) being 0.8:0.2:0.05. The thickness of the light-emittinglayer 1113 was 40 nm.

Then, over the light-emitting layer 1113, 2mDBTPDBq-II (abbreviation)was deposited by evaporation to a thickness of 20 nm and thenbathophenanthroline (abbreviation: BPhen) was deposited by evaporationto a thickness of 20 nm, whereby the electron-transport layer 1114having a stacked structure was formed. Furthermore, lithium fluoride wasdeposited by evaporation to a thickness of 1 nm over theelectron-transport layer 1114, whereby the electron-injection layer 1115was formed.

Finally, aluminum was deposited by evaporation to a thickness of 200 nmover the electron-injection layer 1115 to form the second electrode 1103serving as a cathode; thus, the light-emitting elements 4 to 7 wereobtained. Note that in all the above evaporation steps, evaporation wasperformed by a resistance-heating method.

Element structures of the light-emitting elements 4 to 7 obtained asdescribed above is shown in Table 8.

TABLE 8 Hole- Hole- Light- Electron- First injection transport emittinginjection Second Electrode Layer Layer Layer Electron-transport LayerLayer Electrode Light- ITSO DBT3P-II:MoO_(x) BPAFLP * 2mDBTPDBq-II BPhenLiF Al emitting (110 nm) (4:2 20 nm) (20 nm) (20 nm) (20 nm) (1 nm) (200nm) Element 4 Light- ** emitting Element 5 Light- *** emitting Element 6Light- **** emitting Element 7 * 2mDBTPDBq-II:NPB:[Ir(dmdppr-P)₂(acac)](0.8:0.2:0.05 40 nm) ** 2mDBTPDBq-II:NPB:[Ir(dmdppr-dmp)₂(acac)](0.8:0.2:0.05 40 nm) *** 2mDBTPDBq-II:NPB:[Ir(dmtppr)₂(dibm)](0.8:0.2:0.05 40 nm) **** 2mDBTPDBq-II:NPB:[Ir(dmdppr-dmp)₂(dibm)](0.8:0.2:0.05 40 nm)

Further, the fabricated light-emitting elements 4 to 7 were sealed in aglove box containing a nitrogen atmosphere so as not to be exposed tothe air (specifically, a sealant was applied onto an outer edge of theelement and heat treatment was performed at 80° C. for 1 hour at thetime of sealing).

<<Operation Characteristics of Light-Emitting Elements 4 to 7>>

Operation characteristics of the fabricated light-emitting elements 4 to7 were measured. Note that the measurement was carried out at roomtemperature (under an atmosphere in which the temperature was kept at25° C.).

FIG. 57 shows current density-luminance characteristics of thelight-emitting elements 4 to 7. In FIG. 57, the vertical axis representsluminance (cd/m²) and the horizontal axis represents current density(mA/cm²). FIG. 58 shows voltage-luminance characteristics of thelight-emitting elements 4 to 7. In FIG. 58, the vertical axis representsluminance (cd/m²) and the horizontal axis represents voltage (V).Further, FIG. 59 shows luminance-current efficiency characteristics ofthe light-emitting elements 4 to 7. In FIG. 59, the vertical axisrepresents current efficiency (cd/A) and the horizontal axis representsluminance (cd/m²). FIG. 60 shows voltage-current characteristics of thelight-emitting elements 4 to 7. In FIG. 60, the vertical axis representscurrent (mA) and the horizontal axis represents voltage (V).

FIG. 59 reveals high efficiency of the light-emitting elements 4 to 7respectively including, in part of their light-emitting layers,[Ir(dmdppr-P)₂(acac)] (abbreviation) represented by Structural Formula(121), [Ir(dmdppr-dmp)₂(acac)] (abbreviation) represented by StructuralFormula (122), [Ir(dmtppr)₂(dibm)] (abbreviation) represented byStructural Formula (123), and [Ir(dmdppr-dmp)₂(dibm)] (abbreviation)represented by Structural Formula (124), which are the organometalliccomplexes that are embodiments of the present invention. Table 9 showsinitial values of main characteristics of the light-emitting elements 4to 7 at a luminance of about 1000 cd/m².

TABLE 9 Current Current Power Quantum Voltage Current DensityChromaticity Luminance Efficiency Efficiency Efficiency (V) (mA)(mA/cm²) (x, y) (cd/m²) (cd/A) (lm/W) (%) Light- 3.9 0.22 5.5 (0.68,0.32) 1100 20 16 25 emitting Element 4 Light- 3.3 0.1 2.5 (0.66, 0.34)1000 40 38 29 emitting Element 5 Light- 3.3 0.19 4.8 (0.68, 0.32) 920 1918 23 emitting Element 6 Light- 3.3 0.088 2.2 (0.66, 0.34) 850 38 37 27emitting Element 7

The above results show that the light-emitting elements 4 to 7fabricated in this example are high-luminance light-emitting elementshaving high current efficiency. Moreover, as for color purity, it can befound that the light-emitting elements exhibit reddish orange lightemission with excellent color purity.

FIG. 61 shows emission spectra when a current at a current density of2.5 mA/cm² was supplied to the light-emitting elements 4 to 7. As shownin FIG. 61, the emission spectra of the light-emitting elements 5 and 7each have a peak at around 617 nm, and the emission spectra of thelight-emitting elements 4 and 6 each have a peak at around 630 nm. It isthus indicated that the peaks are derived from emission of theorganometallic complexes each included in the light-emitting elements.In addition, it was observed that half widths of the emission spectra ofthe light-emitting elements 4 to 7 are small. This can be presumed to bean effect brought about by the structure of each of the organometalliccomplexes used in this example, in which methyl groups are bonded to the2-position and the 4-position of the phenyl group bonded to iridium.Therefore, it can be said that the light-emitting elements 4 to 7 havehigh emission efficiency and achieve high color purity.

The light-emitting elements 4 to 7 were subjected to reliability tests.Results of the reliability tests are shown in FIG. 62 and FIG. 63. InFIG. 62, the vertical axis represents normalized luminance (%) with aninitial luminance of 100% and the horizontal axis represents drivingtime (h) of the element. Note that in one of the reliability tests, thelight-emitting elements 4 to 7 were driven under the conditions wherethe initial luminance was set to 5000 cd/m² and the current density wasconstant. As a result, the light-emitting element 4 kept about 60% ofthe initial luminance after 100 hours elapsed; the light-emittingelement 5 kept about 88% of the initial luminance after 38 hourselapsed; the light-emitting element 6 kept about 80% of the initialluminance after 40 hours elapsed; and the light-emitting element 7 keptabout 86% of the initial luminance after 39 hours elapsed. Further, inFIG. 63, the vertical axis represents normalized luminance (%) with aninitial luminance of 100% and the horizontal axis represents drivingtime (h) of the element. Note that in the other of the reliabilitytests, the light-emitting elements 4 to 7 were driven with a currentvalue of 0.3 mA. As a result, the light-emitting element 4 kept about86% of the initial luminance after 100 hours elapsed; the light-emittingelement 5 kept about 91% of the initial luminance after 100 hourselapsed; the light-emitting element 6 kept about 90% of the initialluminance after 100 hours elapsed; and the light-emitting element 7 keptabout 86% of the initial luminance after 100 hours elapsed.

Thus, both of the reliability tests which were conducted under differentconditions showed that the light-emitting elements 4 to 7 are highlyreliable. In addition, it was confirmed that with the use of theorganometallic complex that is one embodiment of the present invention,a light-emitting element with a long lifetime can be obtained.

Example 14 Synthesis Example 9

In Synthesis Example 9, a synthesis method ofbis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-2-pyrimidinyl-κN]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III) (abbreviation: [Ir(dmppm2-dmp)₂(acac)]), theorganometallic complex which is one embodiment of the present inventionrepresented by Structural Formula (126) in Embodiment 1, is described.The structure of [Ir(dmppm2-dmp)₂(acac)] (abbreviation) is shown below.

Step 1: Synthesis of 5-Bromo-2-(3,5-dimethylphenyl)pyrimidine

First, 2.97 g of 5-bromo-2-iodopyrimidine, 1.62 g of3,5-dimethylphenylboronic acid, 1.21 g of sodium carbonate, 0.093 g ofbis(triphenylphosphine)palladium(II) dichloride (Pd(PPh₃)₂Cl₂), 20 mL ofwater, and 20 mL of acetonitrile were put into a recovery flask equippedwith a reflux pipe, and the mixture was bubbled with argon for 15minutes. This reaction container was subjected to irradiation withmicrowaves (2.45 GHz, 100 W) for 1 hour to be heated. Here, into theflask were further put 0.40 g of 3,5-dimethylphenylboronic acid, 0.30 gof sodium carbonate, and 0.024 g of Pd(PPh₃)₂Cl₂, and the mixture wasbubbled with argon for 15 minutes. This reaction container was subjectedto irradiation with microwaves (2.45 GHz, 100 W) again for 1 hour to beheated.

Then, water was added to this solution and the organic layer wasextracted with dichloromethane. The obtained organic layer was washedwith water and saturated brine, and was dried with magnesium sulfate.After the drying, the solution was filtered. The solvent of thissolution was distilled off, and the obtained residue was purified byflash column chromatography using hexane and ethyl acetate as adeveloping solvent in a ratio of 5:1. The solid obtained byconcentration of a fraction was purified by flash column chromatographyusing dichloromethane and hexane as a developing solvent in a ratio of1:1, so that the pyrimidine derivative to be produced was obtained as awhite powder in a yield of 33%. Note that the irradiation withmicrowaves was performed using a microwave synthesis system (Discover,manufactured by CEM Corporation). A synthesis scheme of Step 1 is shownin (i-1).

Step 2: Synthesis of5-(2,6-Dimethylphenyl)-2-(3,5-dimethylphenyl)pyrimidine (abbreviation:Hdmppm2-dmp)

Then, 0.91 g of 5-bromo-2-(3,5-dimethylphenyl)pyrimidine, 1.05 g of2,6-dimethylphenylboronic acid, 0.74 g of sodium carbonate, 0.029 g ofbis(triphenylphosphine)palladium(II) dichloride (Pd(PPh₃)₂Cl₂), 13 mL ofwater, and 13 mL of acetonitrile were put into a recovery flask equippedwith a reflux pipe, and the mixture was bubbled with argon for 15minutes. This reaction container was subjected to irradiation withmicrowaves (2.45 GHz, 100 W) for 4 hours to be heated. Here, into theflask were further put 1.07 g of 2,6-dimethylphenylboronic acid, 0.73 gof sodium carbonate, and 0.029 g of Pd(PPh₃)₂Cl₂, and the mixture wasbubbled with argon for 15 minutes. This reaction container was subjectedto irradiation with microwaves (2.45 GHz, 100 W) again for 3 hours to beheated. After that, the obtained mixture was suction-filtered withwater. The obtained solid was purified by flash column chromatographyusing toluene and hexane as a developing solvent in a ratio of 1:1, sothat Hdmppm2-dmp (abbreviation), which was the pyrimidine derivative tobe produced, was obtained as a white powder in a yield of 83%. Asynthesis scheme of Step 2 is shown in (i-2).

Step 3: Synthesis of Di-μ-chloro-tetrakis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-2-pyrimidinyl-κN]phenyl-κC}diiridium(III)(abbreviation: [Ir(dmppm2-dmp)₂Cl]₂)

Next, into a recovery flask equipped with a reflux pipe were put 15 mLof 2-ethoxyethanol, 5 mL of water, 0.83 g of Hdmppm2-dmp (abbreviation)obtained in Step 2, and 0.39 g of iridium chloride hydrate (IrCl₃.H₂O)(produced by Sigma-Aldrich Corporation), and the air in the flask wasreplaced with argon. After that, irradiation with microwaves (2.45 GHz,100 W) was performed for 1 hour to cause a reaction. The solvent wasdistilled off, and then the obtained residue was suction-filtered andwashed with hexane to give [Ir(dmppm2-dmp)₂Cl]₂ (abbreviation) that is adinuclear complex as a brown powder in a yield of 91%. A synthesisscheme of Step 3 is shown in (i-3).

Step 4: Synthesis ofBis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-2-pyrimidinyl-κN]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III) (abbreviation: [Ir(dmppm2-dmp)₂(acac)])

Next, into a recovery flask equipped with a reflux pipe were put 30 mLof 2-ethoxyethanol, 0.95 g of [Ir(dmppm2-dmp)₂Cl]₂ (abbreviation) thatis the dinuclear complex obtained in Step 3, 0.18 g of acetylacetone(abbreviation: Hacac), and 0.63 g of sodium carbonate, and the air inthe flask was replaced with argon. Then, irradiation with microwaves(2.45 GHz, 120 W) was performed for 60 minutes. Here, 0.18 g of Hacacwas added, and irradiation with microwaves (2.45 GHz, 200 W) wasperformed again for 60 minutes so that heating was performed. Thesolvent was distilled off, and the obtained residue was suction-filteredwith methanol. The obtained solid was washed with water and methanol.After the obtained solid was purified by flash column chromatographyusing hexane and ethyl acetate as a developing solvent in a ratio of5:1, recrystallization was carried out with a mixed solvent ofdichloromethane and methanol; thus, [Ir(dmppm2-dmp)₂(acac)](abbreviation), the organometallic complex that is one embodiment of thepresent invention, was obtained as a yellow orange powder in a yield of14%. A synthesis scheme of Step 4 is shown in (i-4).

An analysis result by nuclear magnetic resonance (¹H-NMR) spectroscopyof the yellow orange powder obtained in Step 4 is described below. FIG.64 shows the ¹H-NMR chart. These results revealed that[Ir(dmppm2-dmp)₂(acac)] (abbreviation), the organometallic complex whichis one embodiment of the present invention represented by StructuralFormula (126), was obtained in Synthesis Example 9.

¹H-NMR. δ(CDCl₃): 1.58 (s, 6H), 1.62 (s, 6H), 2.03 (s, 6H), 2.15 (s,6H), 2.28 (s, 6H), 5.17 (s, 1H), 6.63 (d, 2H), 7.15 (t, 4H), 7.24 (t,2H), 7.81 (d, 2H), 8.39 (d, 2H), 8.53 (d, 2H).

Example 15 Synthesis Example 10

In Synthesis Example 10, a synthesis method of bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmppm-dmp)₂(acac)]), the organometallic complex whichis one embodiment of the present invention represented by StructuralFormula (127) in Embodiment 1, is described. The structure of[Ir(dmppm-dmp)₂(acac)] (abbreviation) is shown below.

Step 1: Synthesis of 4-Chloro-6-(3,5-dimethylphenyl)pyrimidine

First, 5.05 g of 4,6-dichloropyrimidine, 5.08 g of3,5-dimethylphenylboronic acid, 3.57 g of sodium carbonate, 0.14 g ofbis(triphenylphosphine)palladium(II) dichloride (Pd(PPh₃)₂Cl₂), 20 mL ofacetonitrile, and 20 mL of water were put into a round-bottom flaskequipped with a reflux pipe, and the mixture was bubbled with argon for15 minutes. Then, heating was performed by irradiation with microwaves(2.45 GHz, 100 W) for 1 hour. After the heating, 2.54 g of3,5-dimethylphenylboronic acid, 1.79 g of sodium carbonate, and 0.066 gof Pd(PPh₃)₂Cl₂ were added, and the mixture was bubbled with argon for15 minutes.

Then, heating was performed by irradiation with microwaves (2.45 GHz,100 W) for 1 hour. After the heating, 1.27 g of3,5-dimethylphenylboronic acid and 0.091 g of Pd(PPh₃)₂Cl₂ were added,and the mixture was bubbled with argon for 15 minutes. Further, heatingwas performed by irradiation with microwaves (2.45 GHz, 100 W) for 1hour. An organic layer was extracted with dichloromethane, and thesolution of the extract was washed with water and saturated brine anddried with magnesium sulfate. After the drying, the solution wasfiltered. The solvent of this solution was distilled off, and then theobtained residue was purified by silica gel column chromatography usingdichloromethane as a developing solvent, so that the pyrimidinederivative to be produced was obtained as a yellow crystal in a yield of31%. Note that the irradiation with microwaves was performed using amicrowave synthesis system (Discover, manufactured by CEM Corporation).A synthesis scheme of Step 1 is shown in (j-1).

Step 2: Synthesis of6-(2,6-Dimethylphenyl)-4-(3,5-dimethylphenyl)pyrimidine (abbreviation:Hdmppm-dmp)

Next, 1.18 g of 4-chloro-6-(3,5-dimethylphenyl)pyrimidine obtained inStep 1, 0.754 g of 2,6-dimethylphenylboronic acid, 0.535 g of sodiumcarbonate, 0.036 g of bis(triphenylphosphine)palladium(II) dichloride(Pd(PPh₃)₂Cl₂), 10 mL of acetonitrile, and 10 mL of water were put intoa round-bottom flask equipped with a reflux pipe, and the mixture wasbubbled with argon for 15 minutes. Heating was performed by irradiationwith microwaves (2.45 GHz, 100 W) for 1 hour. Further, 0.380 g of2,6-dimethylphenylboronic acid, 0.268 g of sodium carbonate, and 0.020 gof Pd(PPh₃)₂Cl₂ were added, and the mixture was bubbled with argon for15 minutes.

Then, heating was performed by irradiation with microwaves (2.45 GHz,100 W) for 3 hours. Then, 0.404 g of 2,6-dimethylphenylboronic acid,0.277 g of sodium carbonate, and 0.019 g of Pd(PPh₃)₂Cl₂ were added, andthe mixture was bubbled with argon for 15 minutes. Heating was performedby irradiation with microwaves (2.45 GHz, 100 W) for 3 hours. Inaddition, 10 mL of acetonitrile and 10 mL of water were added andheating was performed by irradiation with microwaves (2.45 GHz, 100 W)for 3 hours. An organic layer was extracted with dichloromethane, andthe solution of the extract was washed with water and saturated brineand dried with magnesium sulfate. After the drying, the solution wasfiltered. The solvent of this solution was distilled off to give aresidue.

In a similar manner, 1.13 g of 4-chloro-6-(3,5-dimethylphenyl)pyrimidineobtained in Step 1, 0.802 g of 2,6-dimethylphenylboronic acid, 0.548 gof sodium carbonate, 0.040 g of Pd(PPh₃)₂Cl₂, 20 mL of acetonitrile, and20 mL of water were put into a round-bottom flask equipped with a refluxpipe, and the mixture was bubbled with argon for 15 minutes. Then,heating was performed by irradiation with microwaves (2.45 GHz, 100 W)for 2 hours. Further, 0.408 g of 2,6-dimethylphenylboronic acid, 0.288 gof sodium carbonate, and 0.021 g of Pd(PPh₃)₂Cl₂ were added, and themixture was bubbled with argon for 15 minutes.

Then, heating was performed by irradiation with microwaves (2.45 GHz,100 W) for 4 hours. Further, 7 mL of acetonitrile, 0.214 g of2,6-dimethylphenylboronic acid, 0.273 g of sodium carbonate, and 0.020 gof Pd(PPh₃)₂Cl₂ were added, and the mixture was bubbled with argon for15 minutes. Heating was performed by irradiation with microwaves (2.45GHz, 100 W) for 2.5 hours. An organic layer was extracted withdichloromethane, and the solution of the extract was washed with waterand saturated brine and dried with magnesium sulfate. After the drying,the solution was filtered. The solvent of this solution was distilledoff to give a residue.

The obtained two residues were purified by silica gel columnchromatography using dichloromethane as a developing solvent. The solidobtained by concentration of a fraction was dissolved in dichloromethaneand filtered through a filter aid in which Celite, alumina, and Celitewere stacked in that order to give 0.3 g of a crude crystal (yellow).

After that, 1.10 g of 4-chloro-6-(3,5-dimethylphenyl)pyrimidine obtainedby the above silica gel column chromatography, 0.753 g of2,6-dimethylphenylboronic acid, 0.534 g of sodium carbonate, 0.038 g ofPd(PPh₃)₂Cl₂, 20 mL of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)pyrimidinone(abbreviation: DMPU), and 20 mL of water were put into a round-bottomflask equipped with a reflux pipe, and the mixture was bubbled withargon for 15 minutes. Then, heating was performed by irradiation withmicrowaves (2.45 GHz, 100 W) for 1 hour. Further, 0.376 g of2,6-dimethylphenylboronic acid, 0.269 g of sodium carbonate, and 0.011 gof Pd(PPh₃)₂Cl₂ were added, and the mixture was bubbled with argon for15 minutes.

Next, heating was performed by irradiation with microwaves (2.45 GHz,100 W) for 2 hours. An organic layer was extracted with dichloromethane,and the solution of the extract was washed with water and saturatedbrine and dried with magnesium sulfate. After the drying, the solutionwas filtered. The solvent of this solution was distilled off to give aresidue. This residue and the yellow crude crystal were combined andpurified by silica gel column chromatography using dichloromethane andethyl acetate as a developing solvent to give Hdmppm-dmp (abbreviation),which was the pyrimidine derivative to be produced, as a yellow oilysubstance in a yield of 34%. A synthesis scheme of Step 2 is shown in(j-2).

Step 3: Synthesis of Di-μ-chloro-tetrakis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}diiridium(III)(abbreviation: [Ir(dmppm-dmp)₂Cl]₂)

Next, into a round-bottom flask equipped with a reflux pipe were put 30mL of 2-ethoxyethanol, 10 mL of water, 1.00 g of Hdmppm-dmp(abbreviation) obtained in Step 2, and 0.568 g of iridium chloridehydrate (IrCl₃.H₂O) (produced by Sigma-Aldrich Corporation), and the airin the flask was replaced with argon. After that, irradiation withmicrowaves (2.45 GHz, 100 W) was performed for 1 hour to cause areaction. The solvent was distilled off, and then the obtained residuewas suction-filtered and washed with hexane to give [Ir(dmppm-dmp)₂Cl]₂(abbreviation) that is a dinuclear complex as a black solid in a yieldof 79%. A synthesis scheme of Step 3 is shown in (j-3).

Step 4: Synthesis ofBis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmppm-dmp)₂(acac)])

Next, into a round-bottom flask equipped with a reflux pipe were put 30mL of 2-ethoxyethanol, 0.606 g of [Ir(dmppm-dmp)₂Cl]₂ (abbreviation)that is the dinuclear complex obtained in Step 3, 0.138 g ofacetylacetone (abbreviation: Hacac), and 0.489 g of sodium carbonate,and the air in the flask was replaced with argon. After that, heatingwas performed by irradiation with microwaves (2.45 GHz, 120 W) for 1hour. The solvent was distilled off, and the obtained residue waspurified by flash column chromatography using ethyl acetate and hexaneas a developing solvent in a ratio of 1:2. Then, recrystallization wascarried out with a mixed solvent of dichloromethane and hexane; thus,[Ir(dmppm-dmp)₂(acac)] (abbreviation), the organometallic complex thatis one embodiment of the present invention, was obtained as a dark redpowder in a yield of 50%. A synthesis scheme of Step 4 is shown in(j-4).

An analysis result by nuclear magnetic resonance (¹H-NMR) spectroscopyof the dark red powder obtained in Step 4 is described below. FIG. 65shows the ¹H-NMR chart. These results revealed that[Ir(dmppm-dmp)₂(acac)] (abbreviation), the organometallic complex whichis one embodiment of the present invention represented by StructuralFormula (127), was obtained in Synthesis Example 10.

¹H-NMR. δ(DMSO-d6): 1.43 (s, 6H), 1.70 (s, 6H), 2.19 (s, 12H), 2.18 (s,6H), 5.34 (s, 1H), 6.54 (s, 2H), 7.23 (d, 4H), 7.30-7.33 (m, 2H), 7.79(s, 2H), 8.23 (s, 2H), 8.95 (ds, 2H).

Example 16 Synthesis Example 11

In Synthesis Example 11, a synthesis method ofbis{4,6-dimethyl-2-[6-tert-butyl-4-pyrimidinyl-κN3]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(tBudmppm)₂(acac)]), the organometallic complex whichis one embodiment of the present invention represented by StructuralFormula (106) in Embodiment 1, is described. The structure of[Ir(tBudmppm)₂(acac)] (abbreviation) is shown below.

Step 1: Synthesis of 4-tert-Butyl-6-hydroxypyrimidine)

First, 7.2 g of formamidine hydrochloride, 7.5 g of sodium methoxide,and 70 mL of methanol were put into a 100 mL three-neck flask. Then, 10g of methyl 4,4-dimethyl-3-oxovalerate was added to this mixed solution.The mixture was stirred at room temperature for 24 hours. After that, amixed solution of 17 mL of water and 7.2 mL of acetic acid was added tothe reacted solution, and the mixture was stirred at room temperature.This mixture was concentrated, and the resulting residue was dissolvedin water. The solution was subjected to extraction with ethyl acetate.The obtained solution of the extract was washed with saturated brine,and magnesium sulfate was added for drying. After the drying, thesolution was filtered. After the solvent of this solution was distilledoff, the obtained solid was washed with ethyl acetate, so that thepyrimidine derivative to be produced was obtained as a white solid in ayield of 49%. A synthesis scheme of Step 1 is shown in (k-1).

Step 2: Synthesis of 4-tert-Butyl-6-chloropyrimidine)

Next, 4.7 g of 4-tert-butyl-6-hydroxypyrimidine obtained in Step 1 and14 mL of phosphoryl chloride were put into a 50 mL three-neck flask, andthe mixture was heated and refluxed for 1.5 hours. After the reflux,phosphoryl chloride was distilled off under reduced pressure. Theobtained residue was dissolved in dichloromethane, washed with water anda saturated aqueous solution of sodium hydrogen carbonate, and driedwith magnesium sulfate. After the drying, the solution was filtered. Thesolvent of this solution was distilled off, and then the obtainedresidue was purified by silica gel column chromatography using hexaneand ethyl acetate as a developing solvent in a ratio of 10:1, so thatthe pyrimidine derivative to be produced was obtained as a white solidin a yield of 78%. A synthesis scheme of Step 2 is shown in (k-2).

Step 3: Synthesis of 4-tert-Butyl-6-(3,5-dimethylphenyl)pyrimidine(abbreviation: HtBudmppm)

Next, 2.01 g of 4-tert-butyl-6-chloropyrimidine obtained in Step 2, 3.63g of 3,5-dimethylphenylboronic acid, 2.48 g of sodium carbonate, 0.10 gof bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh₃)₂Cl₂), 20 mLof water, and 20 mL of DMF were put into a recovery flask equipped witha reflux pipe, and the mixture was bubbled with argon for 15 minutes.This reaction container was subjected to irradiation with microwaves(2.45 GHz, 100 W) for 60 minutes to be heated. Here, into the flask werefurther put 0.90 g of 3,5-dimethylphenylboronic acid, 0.64 g of sodiumcarbonate, and 0.025 g of Pd(PPh₃)₂Cl₂, and the mixture was bubbled withargon for 15 minutes. This reaction container was subjected toirradiation with microwaves (2.45 GHz, 100 W) again for 60 minutes to beheated. Then, water was added to this solution and the organic layer wasextracted with dichloromethane. The obtained organic layer was washedwith water and saturated brine, and was dried with magnesium sulfate.After the drying, the solution was filtered. The solvent of thissolution was distilled off, and the obtained residue was purified bysilica gel column chromatography using dichloromethane and ethyl acetateas a developing solvent in a ratio of 10:1, so that HtBudmppm(abbreviation), which was the pyrimidine derivative to be produced, wasobtained as a pale yellow oil in a yield of 96%. Note that theirradiation with microwaves was performed using a microwave synthesissystem (Discover, manufactured by CEM Corporation). A synthesis schemeof Step 3 is shown in (k-3).

Step 4: Synthesis ofDi-μ-chloro-tetrakis{4,6-dimethyl-2-[6-tert-butyl-4-pyrimidinyl-κN3]phenyl-κC}diiridium(III)(abbreviation: [Ir(tBudmppm)₂Cl]₂)

Next, into a recovery flask equipped with a reflux pipe were put 30 mLof 2-ethoxyethanol, 10 mL of water, 2.69 g of HtBudmppm (abbreviation)obtained in Step 3, and 1.48 g of iridium chloride hydrate (IrCl₃.H₂O)(produced by Sigma-Aldrich Corporation), and the air in the flask wasreplaced with argon. After that, irradiation with microwaves (2.45 GHz,100 W) was performed for 1 hour to cause a reaction. The solvent wasdistilled off, and then the obtained residue was suction-filtered andwashed with ethanol to give [Ir(tBudmppm)₂Cl]₂ (abbreviation) that is adinuclear complex as a green powder in a yield of 62%. A synthesisscheme of Step 4 is shown in (k-4).

Step 5: Synthesis ofBis{4,6-dimethyl-2-[6-tert-butyl-4-pyrimidinyl-κN3]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(tBudmppm)₂(acac)])

Further, into a recovery flask equipped with a reflux pipe were put 30mL of 2-ethoxyethanol, 0.98 g of [Ir(tBudmppm)₂Cl]₂ (abbreviation) thatis the dinuclear complex obtained in Step 4, 0.21 g of acetylacetone(abbreviation: Hacac), and 0.73 g of sodium carbonate, and the air inthe flask was replaced with argon. Then, irradiation with microwaves(2.45 GHz, 200 W) was performed for 60 minutes. Here, 0.21 g of Hacac(abbreviation) was added, and irradiation with microwaves (2.45 GHz, 100W) was performed again for 60 minutes so that heating was performed. Thesolvent was distilled off, and the obtained residue was suction-filteredwith ethanol. The obtained solid was washed with water and ethanol. Theobtained solid was dissolved in dichloromethane and filtered through afilter aid in which Celite, alumina, and Celite were stacked in thatorder. Then, recrystallization was carried out with a mixed solvent ofdichloromethane and ethanol; thus, [Ir(tBudmppm)₂(acac)] (abbreviation),the organometallic complex that is one embodiment of the presentinvention, was obtained as a yellow orange powder in a yield of 61%. Asynthesis scheme of Step 5 is shown in (k-5).

An analysis result by nuclear magnetic resonance (¹H-NMR) spectroscopyof the yellow orange powder obtained in Step 5 is described below. FIG.66 shows the ¹H-NMR chart. These results revealed that[Ir(tBudmppm)₂(acac)] (abbreviation), the organometallic complex whichis one embodiment of the present invention represented by StructuralFormula (106), was obtained in Synthesis Example 11.

¹H-NMR. δ(CDCl₃): 1.38 (s, 6H), 1.46 (s, 18H), 1.69 (s, 6H), 2.26 (s,6H), 5.17 (s, 1H), 6.55 (s, 2H), 7.43 (s, 2H), 7.71 (s, 2H), 8.87 (s,2H).

REFERENCE NUMERALS

-   101: first electrode, 102: EL layer, 103: second electrode, 111:    hole-injection layer, 112: hole-transport layer, 113: light-emitting    layer, 114: electron-transport layer, 115: electron-injection layer,    116: charge generation layer, 201: anode, 202: cathode, 203: EL    layer, 204: light-emitting layer, 205: phosphorescent compound, 206:    first organic compound, 207: second organic compound, 301: first    electrode, 302(1): first EL layer, 302(2): second EL layer,    302(n−1): (n−1)-th EL layer, 302(n): (n)-th EL layer, 304: second    electrode, 305: charge generation layer (I), 305(1): first charge    generation layer (I), 305(2): second charge generation layer (I),    305(n−2): (n−2)-th charge generation layer (I), 305(n−1): (n−1)-th    charge generation layer (I), 401: reflective electrode, 402:    semi-transmissive and semi-reflective electrode, 403 a: first    transparent conductive layer, 403 b: second transparent conductive    layer, 404B: first light-emitting layer (B), 404G: second    light-emitting layer (G), 404R: third light-emitting layer (R), 405:    EL layer, 410R: first light-emitting element (R), 410G: second    light-emitting element (G), 410B: third light-emitting element (B),    501: element substrate, 502: pixel portion, 503: driver circuit    portion (source line driver circuit), 504 a and 504 b: driver    circuit portion (gate line driver circuit), 505: sealant, 506:    sealing substrate, 507: wiring, 508: FPC (flexible printed circuit),    509: n-channel TFT, 510: p-channel TFT, 511: switching TFT, 512:    current control TFT, 513: first electrode (anode), 514: insulator,    515: EL layer, 516: second electrode (cathode), 517: light-emitting    element, 518: space, 1100: substrate, 1101: first electrode, 1102:    EL layer, 1103: second electrode, 1111: hole-injection layer, 1112:    hole-transport layer, 1113: light-emitting layer, 1114:    electron-transport layer, 1115: electron-injection layer, 7100:    television set, 7101: housing, 7103: display portion, 7105: stand,    7107: display portion, 7109: operation key, 7110: remote controller,    7201: main body, 7202: housing, 7203: display portion, 7204:    keyboard, 7205: external connection port, 7206: pointing device,    7301: housing, 7302: housing, 7303: joint portion, 7304: display    portion, 7305: display portion, 7306: speaker portion, 7307:    recording medium insertion portion, 7308: LED lamp, 7309: operation    key, 7310: connection terminal, 7311: sensor, 7312: microphone,    7400: mobile phone, 7401: housing, 7402: display portion, 7403:    operation button, 7404: external connection port, 7405: speaker,    7406: microphone, 8001: lighting device, 8002: lighting device,    8003: lighting device, 8004: lighting device, 9033: clasp, 9034:    display mode switch, 9035: power switch, 9036: power saver switch,    9038: operation switch, 9630: housing, 9631: display portion, 9631    a: display portion, 9631 b: display portion, 9632 a: touch panel    region, 9632 b: touch panel region, 9633: solar cell, 9634: charge    and discharge control circuit, 9635: battery, 9636: DCDC converter,    9637: operation key, 9638: converter, and 9639: button.

This application is based on Japanese Patent Application serial no.2011-282465 filed with Japan Patent Office on Dec. 23, 2011, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. (canceled)
 2. A compound represented by thefollowing formula:

wherein: R¹ to R⁴ independently represent a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms; and R¹⁴ and R¹⁵ independentlyrepresent hydrogen, a substituted or unsubstituted alkyl group having 1to 6 carbon atoms, or a substituted or unsubstituted phenyl group. 3.The compound according to claim 2, wherein the compound is representedby any one of the following formulae:


4. A light-emitting device comprising: a cathode; an anode; and an ELlayer between the cathode and the anode, the EL layer comprising acompound represented by the following formula:

wherein: R¹ to R⁴ independently represent a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms; and R¹⁴ and R¹⁵ independentlyrepresent hydrogen, a substituted or unsubstituted alkyl group having 1to 6 carbon atoms, or a substituted or unsubstituted phenyl group. 5.The light-emitting device according to claim 4, wherein: the EL layercomprises a light-emitting layer, and the compound is included in thelight-emitting layer.
 6. The light-emitting device according to claim 5,wherein the light-emitting layer further comprises a host material whosetriplet excitation energy is larger than a triplet excitation energy ofthe compound.
 7. The light-emitting device according to claim 5, whereinthe light-emitting layer further comprises a first organic compound anda second organic compound which each have a triplet excitation energyhigher than a triplet excitation energy of the compound.
 8. Thelight-emitting device according to claim 5, wherein the light-emittinglayer further comprises a first organic compound and a second organiccompound which are selected so as to form an exciplex.
 9. Thelight-emitting device according to claim 8, wherein: an absorptionspectrum of the compound overlaps with an emission spectrum of theexciplex; and an emission peak wavelength of the exciplex is longer thanan absorption peak wavelength of the compound.
 10. The light-emittingdevice according to claim 4, wherein: the EL layer comprises a first ELlayer and a second EL layer with a charge-generation layer therebetween;and the compound is included in at least one of the first EL layer andthe second EL layer.
 11. A module comprising: the light-emitting deviceaccording to claim 4; and a flexible printed circuit connected to thelight-emitting device.
 12. A module comprising: the light-emittingdevice according to claim 4; and a tape carrier package connected to thelight-emitting device.
 13. An electronic device comprising: the moduleaccording to claim 11; and a housing equipped with the module.
 14. Anelectronic device comprising: the module according to claim 12; and ahousing equipped with the module.
 15. A lighting device comprising thelight-emitting device according to claim 4.